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. 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. 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 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. These packets are self entities that travel on it's own and doesn't need any medium to sustain it. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How do electromagnetic waves travel in a vacuum?
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Active Oldest Votes. Improve this answer. Clever Clever 1, 8 8 silver badges 13 13 bronze badges. It is interesting what you said about spacetime being some sort of a 'medium'. The metric does not appear in the QED Lagrangian, so how is the claim above justified? Just curious, I'm probably missing something obvious!
It does however in scalar products, i. PhotonBoom PhotonBoom 5, 2 2 gold badges 14 14 silver badges 32 32 bronze badges. This is how the field propagates. This means that electromagnetic waves can travel through air, solid objects and even space. This is how astronauts on spacewalks use radios to communicate. Radio waves are a type of electromagnetic wave. Electricity can be static, like what holds a balloon to the wall or makes your hair stand on end.
Magnetism can also be static like a refrigerator magnet. But when they change or move together, they make waves - electromagnetic waves. Electromagnetic waves are formed when an electric field which is shown in red arrows couples with a magnetic field which is shown in blue arrows. Magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave. When you listen to the radio, watch TV, or cook dinner in a microwave oven, you are using electromagnetic waves.
Furthermore, different materials have their atoms more closely packed and thus the amount of distance between atoms is less. These two factors are dependent upon the nature of the material through which the electromagnetic wave is traveling.
As a result, the speed of an electromagnetic wave is dependent upon the material through which it is traveling. For more information on physical descriptions of waves, visit The Physics Classroom Tutorial. Detailed information is available there on the following topics:. Physics Tutorial.
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