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Electromagnetism (Essentials) - Class 12th

Course: electromagnetism (essentials) - class 12th   >   unit 14.

  • Energy Density
  • Momentum of EM waves

Light: Electromagnetic waves, the electromagnetic spectrum and photons

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Introduction to electromagnetic waves

Basic properties of waves: amplitude, wavelength, and frequency, example: calculating the wavelength of a light wave, the electromagnetic spectrum, quantization of energy and the dual nature of light, example: calculating the energy of a photon, attributions.

  • “ Electromagnetic Radiation ” from UC Davis ChemWiki, CC BY-NC-SA 3.0

Additional References

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Incredible Answer

As you move from left to right on the electromagnetic spectrum, What happens to frequency? What happens to wavelength?

Arrange the following types of electromagnetic waves in order by wavelength, from longest to shortest: Gammarays Visible light Infrared radiation Ultraviolet radiation Microwaves Radio waves X-ray

What kinds of electromagnetic waves have the lowest frequencies? What kinds have the highest frequencies?

Which type of electromagnetic waves has more energy, an ultraviolet wave or an infrared wave? How can you tell this by looking at the electromagnetic spectrum?

In terms of wavelength and frequency, What is the difference between a radio wave and an X-ray?

Based on your results, which type of electromagnetic wave do you think is more dangerous, a low-frequency wave or a high-frequency wave? Why?

  • Match visual representations of waves to their written descriptions.
  • Identify and describe the parts of the electromagnetic spectrum.
  • Compare and order different types of electromagnetic waves by frequency, wavelength, and energy.

image

  • Wavelength:
  • Information:

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Anatomy of an Electromagnetic Wave

Energy, a measure of the ability to do work, comes in many forms and can transform from one type to another. Examples of stored or potential energy include batteries and water behind a dam. Objects in motion are examples of kinetic energy. Charged particles—such as electrons and protons—create electromagnetic fields when they move, and these fields transport the type of energy we call electromagnetic radiation, or light.

A photograph of a drop of water leaving ripples in a pool.

What are Electromagnetic and Mechanical waves?

Mechanical waves and electromagnetic waves are two important ways that energy is transported in the world around us. Waves in water and sound waves in air are two examples of mechanical waves. Mechanical waves are caused by a disturbance or vibration in matter, whether solid, gas, liquid, or plasma. Matter that waves are traveling through is called a medium. Water waves are formed by vibrations in a liquid and sound waves are formed by vibrations in a gas (air). These mechanical waves travel through a medium by causing the molecules to bump into each other, like falling dominoes transferring energy from one to the next. Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves.

An illustration in 3 panels — the first panel shows a wave approaching an insect sitting on the surface of the water. Second panel shows the wave passing underneath the insect, the insect stays in the same place but moves up as the wave passes. Third panel shows that the insect did not move with the wave, instead the wave had passed by the insect.

ELECTROMAGNETIC WAVES

Electricity can be static, like the energy that can make your hair stand on end. Magnetism can also be static, as it is in a refrigerator magnet. A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.

In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves. He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. He summarized this relationship between electricity and magnetism into what are now referred to as "Maxwell's Equations."

A diagram of an electric field shown as a sine wave with red arrows beneath the curves and a magnetic field shown as a sine wave with blue arrows perpendicular to the electric field.

Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz.

His experiment with radio waves solved two problems. First, he had demonstrated in the concrete, what Maxwell had only theorized — that the velocity of radio waves was equal to the velocity of light! This proved that radio waves were a form of light! Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves — electromagnetic waves.

WAVES OR PARTICLES? YES!

Light is made of discrete packets of energy called photons. Photons carry momentum, have no mass, and travel at the speed of light. All light has both particle-like and wave-like properties. How an instrument is designed to sense the light influences which of these properties are observed. An instrument that diffracts light into a spectrum for analysis is an example of observing the wave-like property of light. The particle-like nature of light is observed by detectors used in digital cameras—individual photons liberate electrons that are used for the detection and storage of the image data.

POLARIZATION

One of the physical properties of light is that it can be polarized. Polarization is a measurement of the electromagnetic field's alignment. In the figure above, the electric field (in red) is vertically polarized. Think of a throwing a Frisbee at a picket fence. In one orientation it will pass through, in another it will be rejected. This is similar to how sunglasses are able to eliminate glare by absorbing the polarized portion of the light.

DESCRIBING ELECTROMAGNETIC ENERGY

The terms light, electromagnetic waves, and radiation all refer to the same physical phenomenon: electromagnetic energy. This energy can be described by frequency, wavelength, or energy. All three are related mathematically such that if you know one, you can calculate the other two. Radio and microwaves are usually described in terms of frequency (Hertz), infrared and visible light in terms of wavelength (meters), and x-rays and gamma rays in terms of energy (electron volts). This is a scientific convention that allows the convenient use of units that have numbers that are neither too large nor too small.

The number of crests that pass a given point within one second is described as the frequency of the wave. One wave—or cycle—per second is called a Hertz (Hz), after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz.

Diagram showing frequency as the measurement of the number of wave crests that pass a given point in a second. Wavelength is measured as the distance between two crests.

Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet!

An illustration showing a jump rope with each end being held by a person. As the people move the jump rope up and down very fast – adding MORE energy – the more wave crests appear, thus shorter wavelengths. When the people move the jump rope up and down slower, there are fewer wave crests within the same distance, thus longer wavelengths.

An electromagnetic wave can also be described in terms of its energy—in units of measure called electron volts (eV). An electron volt is the amount of kinetic energy needed to move an electron through one volt potential. Moving along the spectrum from long to short wavelengths, energy increases as the wavelength shortens. Consider a jump rope with its ends being pulled up and down. More energy is needed to make the rope have more waves.

Next: Wave Behaviors

National Aeronautics and Space Administration, Science Mission Directorate. (2010). Anatomy of an Electromagnetic Wave. Retrieved [insert date - e.g. August 10, 2016] , from NASA Science website: http://science.nasa.gov/ems/02_anatomy

Science Mission Directorate. "Anatomy of an Electromagnetic Wave" NASA Science . 2010. National Aeronautics and Space Administration. [insert date - e.g. 10 Aug. 2016] http://science.nasa.gov/ems/02_anatomy

Discover More Topics From NASA

James Webb Space Telescope

The image is divided horizontally by an undulating line between a cloudscape forming a nebula along the bottom portion and a comparatively clear upper portion. Speckled across both portions is a starfield, showing innumerable stars of many sizes. The smallest of these are small, distant, and faint points of light. The largest of these appear larger, closer, brighter, and more fully resolved with 8-point diffraction spikes. The upper portion of the image is blueish, and has wispy translucent cloud-like streaks rising from the nebula below. The orangish cloudy formation in the bottom half varies in density and ranges from translucent to opaque. The stars vary in color, the majority of which have a blue or orange hue. The cloud-like structure of the nebula contains ridges, peaks, and valleys – an appearance very similar to a mountain range. Three long diffraction spikes from the top right edge of the image suggest the presence of a large star just out of view.

Perseverance Rover

electromagnetic waves travel at quizlet

Parker Solar Probe

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Introduction to Electromagnetic Waves

Chapter outline.

The beauty of a coral reef, the warm radiance of sunshine, the sting of sunburn, the X-ray revealing a broken bone, even microwave popcorn—all are brought to us by electromagnetic waves . The list of the various types of electromagnetic waves, ranging from radio transmission waves to nuclear gamma-ray ( γ γ -ray) emissions, is interesting in itself.

Even more intriguing is that all of these widely varied phenomena are different manifestations of the same thing—electromagnetic waves. (See Figure 24.2 .) What are electromagnetic waves? How are they created, and how do they travel? How can we understand and organize their widely varying properties? What is their relationship to electric and magnetic effects? These and other questions will be explored.

Misconception Alert: Sound Waves vs. Radio Waves

Many people confuse sound waves with radio waves , one type of electromagnetic (EM) wave. However, sound and radio waves are completely different phenomena. Sound creates pressure variations (waves) in matter, such as air or water, or your eardrum. Conversely, radio waves are electromagnetic waves , like visible light, infrared, ultraviolet, X-rays, and gamma rays. EM waves don’t need a medium in which to propagate; they can travel through a vacuum, such as outer space.

A radio works because sound waves played by the D.J. at the radio station are converted into electromagnetic waves, then encoded and transmitted in the radio-frequency range. The radio in your car receives the radio waves, decodes the information, and uses a speaker to change it back into a sound wave, bringing sweet music to your ears.

Discovering a New Phenomenon

It is worth noting at the outset that the general phenomenon of electromagnetic waves was predicted by theory before it was realized that light is a form of electromagnetic wave. The prediction was made by James Clerk Maxwell in the mid-19th century when he formulated a single theory combining all the electric and magnetic effects known by scientists at that time. “Electromagnetic waves” was the name he gave to the phenomena his theory predicted.

Such a theoretical prediction followed by experimental verification is an indication of the power of science in general, and physics in particular. The underlying connections and unity of physics allow certain great minds to solve puzzles without having all the pieces. The prediction of electromagnetic waves is one of the most spectacular examples of this power. Certain others, such as the prediction of antimatter, will be discussed in later modules.

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Electromagnetic waves are a form of radiation that travel though the universe. They are formed when an electric field (Fig. 1 red arrows) couples with a magnetic field (Fig.1 blue arrows).

Both electricity and magnetism can be static (respectively, what holds a balloon to the wall or a refrigerator magnet to metal), but when they change or move together, they make waves. Magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave.

Unlike sound waves, which must travel through matter by bumping molecules into each other like dominoes (and thus can not travel through a vacuum like space), electromagnetic waves do not need molecules to travel. They can travel through air, solid objects, and even space, making them very useful for a lot of technologies.

When you listen to the radio, connect to a wireless network, or cook dinner in a microwave oven, you are using electromagnetic waves. Radio waves and microwaves are two types of electromagnetic waves. They only differ from each other in wavelength – the distance between one wave crest to the next.

While most of this energy is invisible to us, we can see the range of wavelengths that we call light. This visible part of the electromagnetic spectrum consists of the colors that we see in a rainbow – red, orange, yellow, green, blue, indigo, and violet. Each of these colors also corresponds to a different measurable wavelength of light.

Waves in the electromagnetic spectrum vary in size from very long radio waves that are the length of buildings to very short gamma-rays that are smaller than the nucleus of an atom.

Their size is related to their energy. The smaller the wavelength, the higher the energy. For example, a brick wall blocks the relatively larger and lower-energy wavelengths of visible light but not the smaller, more energetic x-rays. A denser material such as lead, however, can block x-rays.

While it’s commonly said that waves are "blocked" by certain materials, the correct understanding is that wavelengths of energy are absorbed by the material. This understanding is critical to interpreting data from weather satellites because the atmosphere also absorbs some wavelengths while allowing others to pass through.

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Powering Planes With Microwaves Is Not the Craziest Idea

Imagine it’s 2050 and you’re on a cross-country flight on a new type of airliner, one with no fuel on board. The plane takes off, and you rise above the airport. Instead of climbing to cruising altitude, though, your plane levels out and the engines quiet to a low hum. Is this normal? No one seems to know. Anxious passengers crane their necks to get a better view out their windows. They’re all looking for one thing.

Then it appears: a massive antenna array on the horizon. It’s sending out a powerful beam of electromagnetic radiation pointed at the underside of the plane. After soaking in that energy, the engines power up, and the aircraft continues its climb. Over several minutes, the beam will deliver just enough energy to get you to the next ground antenna located another couple hundred kilometers ahead.

The person next to you audibly exhales. You sit back in your seat and wait for your drink. Old-school EV-range anxiety is nothing next to this.

Electromagnetic waves on the fly

Beamed power for aviation is, I admit, an outrageous notion. If physics doesn’t forbid it, federal regulators or nervous passengers probably will. But compared with other proposals for decarbonizing aviation, is it that crazy?

Batteries, hydrogen, alternative carbon-based fuels—nothing developed so far can store energy as cheaply and densely as fossil fuels, or fully meet the needs of commercial air travel as we know it. So, what if we forgo storing all the energy on board and instead beam it from the ground? Let me sketch what it would take to make this idea fly.

Beamed Power for Aviation

For the wireless-power source, engineers would likely choose microwaves because this type of electromagnetic radiation can pass unruffled through clouds and because receivers on planes could absorb it completely, with nearly zero risk to passengers.

To power a moving aircraft, microwave radiation would need to be sent in a tight, steerable beam. This can be done using technology known as a phased array , which is commonly used to direct radar beams. With enough elements spread out sufficiently and all working together, phased arrays can also be configured to focus power on a point a certain distance away, such as the receiving antenna on a plane.

Phased arrays work on the principle of constructive and destructive interference. The radiation from the antenna elements will, of course, overlap. In some directions the radiated waves will interfere destructively and cancel out one another, and in other directions the waves will fall perfectly in phase, adding together constructively. Where the waves overlap constructively, energy radiates in that direction, creating a beam of power that can be steered electronically.

How far we can send energy in a tight beam with a phased array is governed by physics—specifically, by something called the diffraction limit. There’s a simple way to calculate the optimal case for beamed power: D1 D2 > λ R. In this mathematical inequality, D1 and D2 are the diameters of the sending and receiving antennas, λ is the wavelength of the radiation, and R is the distance between those antennas.

Now, let me offer some ballpark numbers to figure out how big the transmitting antenna (D1) must be. The size of the receiving antenna on the aircraft is probably the biggest limiting factor. A medium-size airliner has a wing and body area of about 1,000 square meters, which should provide for the equivalent of a receiving antenna that’s 30 meters wide (D2) built into the underside of the plane.

If physics doesn’t forbid it, federal regulators or nervous passengers probably will.

Next, let’s guess how far we would need to beam the energy. The line of sight to the horizon for someone in an airliner at cruising altitude is about 360 kilometers long, assuming the terrain below is level. But mountains would interfere, plus nobody wants range anxiety , so let’s place our ground antennas every 200 km along the flight path, each beaming energy half of that distance. That is, set R to 100 km.

Finally, assume the microwave wavelength (λ) is 5 centimeters. This provides a happy medium between a wavelength that’s too small to penetrate clouds and one that’s too large to gather back together on a receiving dish. Plugging these numbers into the equation above shows that in this scenario the diameter of the ground antennas (D1) would need to be at least about 170 meters. That’s gigantic, but perhaps not unreasonable. Imagine a series of three or four of these antennas, each the size of a football stadium, spread along the route, say, between LAX and SFO or between AMS and BER.

Power beaming in the real world

While what I’ve described is theoretically possible, in practice engineers have beamed only a fraction of the amount of power needed for an airliner, and they’ve done that only over much shorter distances.

NASA holds the record from an experiment in 1975 , when it beamed 30 kilowatts of power over 1.5 km with a dish the size of a house. To achieve this feat, the team used an analog device called a klystron . The geometry of a klystron causes electrons to oscillate in a way that amplifies microwaves of a particular frequency—kind of like how the geometry of a whistle causes air to oscillate and produce a particular pitch.

Klystrons and their cousins, cavity magnetrons (found in ordinary microwave ovens), are quite efficient because of their simplicity. But their properties depend on their precise geometry, so it’s challenging to coordinate many such devices to focus energy into a tight beam.

In more recent years, advances in semiconductor technology have allowed a single oscillator to drive a large number of solid-state amplifiers in near-perfect phase coordination. This has allowed microwaves to be focused much more tightly than was possible before, enabling more-precise energy transfer over longer distances.

In 2022, the Auckland-based startup Emrod showed just how promising this semiconductor-enabled approach could be. Inside a cavernous hangar in Germany owned by Airbus, the researchers beamed 550 watts across 36 meters and kept over 95 percent of the energy flowing in a tight beam—far better than could be achieved with analog systems. In 2021, the U.S. Naval Research Laboratory showed that these techniques could handle higher power levels when it sent more than a kilowatt between two ground antennas over a kilometer apart. Other researchers have energized drones in the air , and a few groups even intend to use phased arrays to beam solar power from satellites to Earth .

A rectenna for the ages

So beaming energy to airliners might not be entirely crazy. But please remain seated with your seat belts fastened; there’s some turbulence ahead for this idea. A Boeing 737 aircraft at takeoff requires about 30 megawatts—a thousand times as much power as any power-beaming experiment has demonstrated. Scaling up to this level while keeping our airplanes aerodynamic (and flyable) won’t be easy.

Consider the design of the antenna on the plane, which receives and converts the microwaves to an electric current to power the aircraft. This rectifying antenna, or rectenna , would need to be built onto the underside surfaces of the aircraft with aerodynamics in mind. Power transmission will be maximized when the plane is right above the ground station, but it would be far more limited the rest of the time, when ground stations are far ahead or behind the plane. At those angles, the beam would activate only either the front or rear surfaces of the aircraft, making it especially hard to receive enough power.

With 30 MW blasting onto that small of an area, power density will be an issue. If the aircraft is the size of Boeing 737, the rectenna would have to cram about 25 W into each square centimeter. Because the solid-state elements of the array would be spaced about a half-wavelength—or 2.5 cm—apart, this translates to about 150 W per element—perilously close to the maximum power density of any solid-state power-conversion device. The top mark in the 2016 IEEE/Google Little Box Challenge was about 150 W per cubic inch (less than 10 W per cubic centimeter).

The rectenna will also have to weigh very little and minimize the disturbance to the airflow over the plane. Compromising the geometry of the rectenna for aerodynamic reasons might lower its efficiency. State-of-the art power-transfer efficiencies are only about 30 percent, so the rectenna can’t afford to compromise too much.

A Boeing 737 aircraft at takeoff requires about 30 megawatts—a thousand times as much power as any power-beaming experiment has demonstrated.

And all of this equipment will have to work in an electric field of about 7,000 volts per meter—the strength of the power beam. The electric field inside a microwave oven, which is only about a third as strong, can create a corona discharge, or electric arc, between the tines of a metal fork, so just imagine what might happen inside the electronics of the rectenna.

And speaking of microwave ovens, I should mention that, to keep passengers from cooking in their seats, the windows on any beamed-power airplane would surely need the same wire mesh that’s on the doors of microwave ovens—to keep those sizzling fields outside the plane. Birds, however, won’t have that protection.

Fowl flying through our power beam near the ground might encounter a heating of more than 1,000 watts per square meter—stronger than the sun on a hot day. Up higher, the beam will narrow to a focal point with much more heat. But because that focal point would be moving awfully fast and located higher than birds typically fly, any roasted ducks falling from the sky would be rare in both senses of the word. Ray Simpkin, chief science officer at Emrod, told me it’d take “more than 10 minutes to cook a bird” with Emrod’s relatively low-power system.

Legal challenges would surely come, though, and not just from the National Audubon Society. Thirty megawatts beamed through the air would be about 10 billion times as strong as typical signals at 5-cm wavelengths (a band currently reserved for amateur radio and satellite communications). Even if the transmitter could successfully put 99 percent of the waves into a tight beam, the 1 percent that’s leaked would still be a hundred million times as strong as approved transmissions today.

And remember that aviation regulators make us turn off our cellphones during takeoff to quiet radio noise, so imagine what they’ll say about subjecting an entire plane to electromagnetic radiation that’s substantially stronger than that of a microwave oven. All these problems are surmountable, perhaps, but only with some very good engineers (and lawyers).

Compared with the legal obstacles and the engineering hurdles we’d need to overcome in the air, the challenges of building transmitting arrays on the ground, huge as they would have to be, seem modest. The rub is the staggering number of them that would have to be built. Many flights occur over mountainous terrain, producing a line of sight to the horizon that is less than 100 km. So in real-world terrain we’d need more closely spaced transmitters. And for the one-third of airline miles that occur over oceans, we would presumably have to build floating arrays. Clearly, building out the infrastructure would be an undertaking on the scale of the Eisenhower-era U.S. interstate highway system.

Decarbonizing with the world’s largest microwave

People might be able to find workarounds for many of these issues. If the rectenna is too hard to engineer, for example, perhaps designers will find that they don’t have to turn the microwaves back into electricity—there are precedents for using heat to propel airplanes . A sawtooth flight path—with the plane climbing up as it approaches each emitter station and gliding down after it passes by—could help with the power-density and field-of-view issues, as could flying-wing designs, which have much more room for large rectennas. Perhaps using existing municipal airports or putting ground antennas near solar farms could reduce some of the infrastructure cost. And perhaps researchers will find shortcuts to radically streamline phased-array transmitters. Perhaps, perhaps.

To be sure, beamed power for aviation faces many challenges. But less-fanciful options for decarbonizing aviation have their own problems. Battery-powered planes don’t even come close to meeting the needs of commercial airlines. The best rechargeable batteries have about 5 percent of the effective energy density of jet fuel. At that figure, an all-electric airliner would have to fill its entire fuselage with batteries—no room for passengers, sorry—and it’d still barely make it a tenth as far as an ordinary jet. Given that the best batteries have improved by only threefold in the past three decades, it’s safe to say that batteries won’t power commercial air travel as we know it anytime soon .

Any roasted ducks falling from the sky would be rare in both senses of the word.

Hydrogen isn’t much further along, despite early hydrogen-powered flights occurring nearly 40 years ago. And it’s potentially dangerous—enough that some designs for hydrogen planes have included two separate fuselages : one for fuel and one for people to give them more time to get away if the stuff gets explode-y. The same factors that have kept hydrogen cars off the road will probably keep hydrogen planes out of the sky.

Synthetic and biobased jet fuels are probably the most reasonable proposal. They’ll give us aviation just as we know it today, just at a higher cost—perhaps 20 to 50 percent more expensive per ticket. But fuels produced from food crops can be worse for the environment than the fossil fuels they replace, and fuels produced from CO 2 and electricity are even less economical. Plus, all combustion fuels could still contribute to contrail formation, which makes up more than half of aviation’s climate impact.

The big problem with the “sane” approach for decarbonizing aviation is that it doesn’t present us with a vision of the future at all. At the very best, we’ll get a more expensive version of the same air travel experience the world has had since the 1970s.

True, beamed power is far less likely to work. But it’s good to examine crazy stuff like this from time to time. Airplanes themselves were a crazy idea when they were first proposed. If we want to clean up the environment and produce a future that actually looks like a future, we might have to take fliers on some unlikely sounding schemes.

Ian McKay leads Orca Sciences, an applied-science group hosted by Gates Ventures in Seattle and San Francisco. Orca is always looking for new approaches to the future of energy technology. IEEE Spectrum ’s “Not the Craziest Idea” series describes some of these approaches, explains why they’re interesting, and tells readers why they’re too far-fetched to pursue—for now. All opinions expressed herein are McKay’s own and don’t reflect those of Orca, Gates Ventures, or other affiliated parties.

Madhu Gupta

For still another "crazy" idea for decarbonizing aircrafts, how about delivering the power to the aircraft by a microwave beam coming from space-based solar power collecting satellites (already declared dubious in IEEE Spectrum, June 2024)? The receiving antennas would be situated on top of the aircraft instead of their underside, and the footprint of delivered beam would be controlled by satellites. This would eliminate the need for gigantic transmitting antennas on the ground, deliver power even to aircrafts over ocean, and shield the birds flying below the aircraft. Can the dubiousness of two juxtaposed incredulous ideas cancel each other?

Carlos Smith

Interesting article, thanks! The conclusion seems to imply that there is no environmentally friendly way to support the air travel industry. To me it suggests that high-speed rail is the best or only, alternative. Keep the airlines for intercontinental, or cross-continental travel and use high speed rail to replace the more regional flights (and ground traffic as well). Certainly the infrastructure and cost would be much less than contemplated here.

David Metzler

It would only work over land right? At that point you can also use highspeed trains. The only difference is that they drive slightly slower, which is more than compensated by all the boarding and security stuff. Sometimes we appear to invent a design cause it's fun and not cause it solves a problem. We can fix transportation, it just needs investment in a good public infrastructure. Diverting attention and investment by making up non functional concepts like hyperloop or this bird oven seems therefore counterproductive, fails inevitably and leaves us with the status quo (a car based society).

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  4. What kinds of wave make up the electromagnetic spectrum? Diagram

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  5. How electromagnetic waves are formed and travel through spac

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  1. What speed do EM waves travel?

  2. Nature Of Electromagnetic Waves

  3. Maxwells Equations and Electromagnetic Waves

  4. Electromagnetic Waves || 3D Animated explanation || Class 12th physics || Electromagnetic waves ||

  5. Electromagnetic wave travel in medium at a speed of `2.0xx10^8ms^-1`. The relative permeabilit

  6. The electromagnetic waves travel in free space with the velocity of

COMMENTS

  1. Electromagnetic Waves Flashcards

    Electromagnetic Radiation. The transfer of energy by waves traveling through matter or empty space. Electromagnetic Wave. A wave that consists of vibrating electric and magnetic fields. Magnetic Field. Only acts on moving electrons. Electric Field. Acts on all charged particles, moving or not. Transverse Wave.

  2. Electromagnetic Waves Flashcards

    Diffraction. When light waves bounce away from surface which do not absorb them. Reflection of light. Study with Quizlet and memorize flashcards containing terms like Electromagnetic waves can also be called, The transfer of energy by electromagnetic waves., Electromagnetic waves do not need a _________ to travel through. and more.

  3. 26 Flashcards

    Study with Quizlet and memorize flashcards containing terms like single speed, light waves, X-rays and more. ... In free space, electromagnetic waves travel at a A) variety of speeds. B) single speed. C) speed depending on frequency. Click the card to flip 👆 ...

  4. Electromagnetic waves and the electromagnetic spectrum

    And the speed at which these waves travel is the speed of light, c, and by c I mean three times 10 to the eight meters per second, because light is just and Electromagnetic wave, light is a special example, one particular example of Electromagnetic waves, but it is only one example, these waves can have any wavelength.

  5. Electromagnetic Waves

    Introduction. Electromagnetic waves have two components: an oscillating electric field and a perpendicular, comoving magnetic field which oscillates at the same frequency, but with a phase shifted by 90°. They describe the movement of a packet of energy between two points. In the discussion of EM waves, we are normally concerned with its ...

  6. Light: Electromagnetic waves, the electromagnetic spectrum and photons

    Electromagnetic radiation is one of the many ways that energy travels through space. The heat from a burning fire, the light from the sun, the X-rays used by your doctor, as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation. While these forms of energy might seem quite different from one another ...

  7. 15.2 The Behavior of Electromagnetic Radiation

    In a vacuum, all electromagnetic radiation travels at the same incredible speed of 3.00 Ă— 10 8 m/s, which is equal to 671 million miles per hour. This is one of the fundamental physical constants. It is referred to as the speed of light and is given the symbol c. The space between celestial bodies is a near vacuum, so the light we see from the ...

  8. 16.1 Maxwell's Equations and Electromagnetic Waves

    Starting in 1887, he performed a series of experiments that not only confirmed the existence of electromagnetic waves but also verified that they travel at the speed of light. Hertz used an alternating-current RLC (resistor-inductor-capacitor) circuit that resonates at a known frequency f 0 = 1 2 π L C f 0 = 1 2 π L C and connected it to a ...

  9. 23.1: The Electromagnetic Spectrum

    Radio waves are a type of electromagnetic (EM) radiation with wavelengths in the electromagnetic spectrum longer than infrared light. They have have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves, radio waves travel at the speed of light.

  10. 16.7: Electromagnetic Waves (Summary)

    16.3: Plane Electromagnetic Waves. Mechanical waves travel through a medium such as a string, water, or air. Perhaps the most significant prediction of Maxwell's equations is the existence of combined electric and magnetic (or electromagnetic) fields that propagate through space as electromagnetic waves. Because Maxwell's equations hold in ...

  11. Electromagnetic Waves Flashcards

    Study with Quizlet and memorize flashcards containing terms like Electromagnetic Waves, Electromagnetic Radiation, Medium and more. ... All electromagnetic waves travel at the same speed in a vacuum. 300,00km/speed. Earth. At this speed it takes light 8 minutes to travel the 150 million kilometers from the sun to_____.

  12. 5.1 The Behavior of Light

    Figure 5.4 Characterizing Waves. Electromagnetic radiation has wave-like characteristics. The wavelength (λ) is the distance between crests, the frequency (f) is the number of cycles per second, and the speed (c) is the distance the wave covers during a specified period of time (e.g., kilometers per second).

  13. Introduction to the Electromagnetic Spectrum

    What is Electromagnetic energy? Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion.

  14. EM waves and the electromagnetic spectrum

    Electromagnetic waves travel at 300,000,000 metres per second (m/s) through a vacuum. Often a phrase is used to help remember the order of the groups of the electromagnetic spectrum such as Roman ...

  15. Electromagnetic waves Flashcards

    electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays. In a vacuum electromagnetic waves travel at the speed of light, commonly denoted c.

  16. Electromagnetic Waves

    These waves travel outward, or radiate, from the charged particles. Visible light is an electromagnetic wave, as are radio waves, microwaves, infrared waves, ultraviolet waves, and X-ray. All the different types of electromagnetic waves form the electromagnetic spectrum. All electromagnetic waves travel at the same speed in a vacuum ...

  17. 23.2: Electromagnetic Waves and their Properties

    Electromagnetic waves. Electromagnetic radiation, is a form of energy emitted by moving charged particles. As it travels through space it behaves like a wave, and has an oscillating electric field component and an oscillating magnetic field. These waves oscillate perpendicularly to and in phase with one another.

  18. Anatomy of an Electromagnetic Wave

    This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space. In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves. He noticed that electrical fields and magnetic fields can couple together to ...

  19. Ch. 24 Introduction to Electromagnetic Waves

    Sound creates pressure variations (waves) in matter, such as air or water, or your eardrum. Conversely, radio waves are electromagnetic waves, like visible light, infrared, ultraviolet, X-rays, and gamma rays. EM waves don't need a medium in which to propagate; they can travel through a vacuum, such as outer space.

  20. Electromagnetic Waves Flashcards

    Q-Chat. Study with Quizlet and memorize flashcards containing terms like Energy from the sun reaches Earth by traveling in, A wave that can travel through empty space and matter, energy carried by an electromagnetic wave and more.

  21. Electromagnetic waves

    Electromagnetic waves. Download Image. Electromagnetic waves are a form of radiation that travel though the universe. They are formed when an electric field (Fig. 1 red arrows) couples with a magnetic field (Fig.1 blue arrows). Both electricity and magnetism can be static (respectively, what holds a balloon to the wall or a refrigerator magnet ...

  22. 16.2: Maxwell's Equations and Electromagnetic Waves

    Magnetic fields are generated by moving charges or by changing electric fields. This fourth of Maxwell's equations, Equation 16.2.17, encompasses Ampère's law and adds another source of magnetic fields, namely changing electric fields. Maxwell's equations and the Lorentz force law together encompass all the laws of electricity and magnetism.

  23. Electromagnetic waves chapter 12 Flashcards

    radiant energy. The energy carried by an electromagnetic wave is called radiant energy. wave of speed. All electromagnetic waves travel at 300,000 km/s in the vacuum of space. ("Speed of light.") wave of speed. Nothing travels faster than the speed of light. Wavelength and Frequency.

  24. Electromagnetic Waves Could Power Airplanes from the Ground

    Gates Ventures' Orca Sciences founder explains how beaming electromagnetic radiation from ground antennas could power commercial airplanes as a way to decarbonize aviation.