What makes electromagnetic waves different from each other

The speed of light is generally a point of comparison to express that something is fast. But what exactly is the speed of light? Light Going from Earth to the Moon : A beam of light is depicted travelling between the Earth and the Moon in the time it takes a light pulse to move between them: 1. The relative sizes and separation of the Earth—Moon system are shown to scale.

It is just that: the speed of a photon or light particle. The speed of light in a vacuum commonly written as c is ,, meters per second. This is a universal physical constant used in many areas of physics. For example, you might be familiar with the equation:. This is known as the mass-energy equivalence, and it uses the speed of light to interrelate space and time. This not only explains the energy a body of mass contains, but also explains the hindrance mass has on speed.

There are many uses for the speed of light in a vacuum, such as in special relativity, which says that c is the natural speed limit and nothing can move faster than it. However, we know from our understanding of physics and previous atoms that the speed at which something travels also depends on the medium through which it is traveling. The speed at which light propagates through transparent materials air, glass, etc. The refractive index of air is about 1.

As mentioned earlier, the speed of light usually of light in a vacuum is used in many areas of physics. Below is an example of an application of the constant c.

Fast-moving objects exhibit some properties that are counterintuitive from the perspective of classical mechanics. For example, length contracts and time dilates runs slower for objects in motion.

The effects are typically minute, but are noticeable at sufficiently high speeds. Typically, this periodic event is a wave. Most people have experienced the Doppler effect in action. Consider an emergency vehicle in motion, sounding its siren. As it approaches an observer, the pitch of the sound its frequency sounds higher than it actually is.

When the vehicle reaches the observer, the pitch is perceived as it actually is. When the vehicle continues away from the observer, the pitch is perceived as lower than it actually is. From the perspective of an observer inside the vehicle, the pitch of the siren is constant. The Doppler Effect and Sirens : Waves emitted by a siren in a moving vehicle.

A wave of sound is emitted by a moving vehicle every millisecond. Relative to an onlooker behind the vehicle, the second wave is further from the first wave than one would expect, which suggests a lower frequency. The Doppler effect can be caused by any kind of motion. In the example above, the siren moved relative to a stationary observer. If the observer moves relative to the stationary siren, the observer will notice the Doppler effect on the pitch of the siren. Finally, if the medium through which the waves propagate moves, the Doppler effect will be noticed even for a stationary observer.

An example of this phenomenon is wind. Quantitatively, the Doppler effect can be characterized by relating the frequency perceived f to the velocity of waves in the medium c , the velocity of the receiver relative to the medium v r , the velocity of the source relative to the medium v s , and the actual emitted frequency f 0 :.

The Doppler Effect : Wavelength change due to the motion of source. Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic EM radiation. EM radiation or photon, which is a quantum of light carries momentum; this momentum is transferred to an object when the radiation is absorbed or reflected. Perhaps one of the most well know examples of the radiation pressure would be comet tails.

Although radiation pressure can be understood using classical electrodynamics, here we will examine the quantum mechanical argument. 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. More energy is needed to make the rope have more waves. Top of Page Next: Wave Behaviors. Anatomy of an Electromagnetic Wave. Retrieved [insert date - e. Science Mission Directorate. National Aeronautics and Space Administration. 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. Classical waves transfer energy without transporting matter through the medium.

Waves in a pond do not carry the water molecules from place to place; rather the wave's energy travels through the water, leaving the water molecules in place, much like a bug bobbing on top of ripples in water. When a balloon is rubbed against a head of hair, astatic electric charge is created causing their individual hairs to repel one another. Credit: Ginger Butcher. Electromagnetic Spectrum Series Series Homepage. Infrared Waves. Reflected Near-Infrared.

Visible Light. Ultraviolet Waves. Earth's Radiation Budget. There is no sound in space because there are no molecules there to transmit the sound waves. Electromagnetic waves are not like sound waves because they do not need molecules to travel. 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. Radio waves, television waves, and microwaves are all types of electromagnetic waves.