# Electro magnetic wave and light

• Mjdgard
In summary: I think that your confusion arises from the fact that there are two "types" of light in the world. One type is what I'll call "light", which is the visible stuff that we see with our eyes. The other type of light is what I'll call "light", which is light of all wavelengths, including the stuff we can't see.In summary, light and electromagnetic waves are two terms used to describe the same phenomenon, varying only in their wavelength and frequency. Photons, which are particles that correspond to an energy quantum, make up both types of light, and can be described as either waves or streams depending on the perspective. The Maxwell equations apply to all types of light, including visible light, X-rays
Mjdgard
Hi

What is the difference between light (photons) and electromagnetic waves (eg radio waves)?
According to some tables (like this ) the only difference is its wave length. But to me this doesen't make sense! i learned, that a photon just acts like a wave. furthermore a photon has got a mass (rest mass=0) , but i never heard this about em-waves.
Uh, and it would be possible to slow down the speed of light if it were a 'normal' em-wave, wouldn't it? Urks...

if it would be possible to compress the wavelength of a radio wave, till it has the same elongation as a light wave (about 500nm), what would happen?
What would i see?

Hmm, i hope you understand my question and hopefully it's not too silly. :)

Mjdgard

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Mjdgard said:
Hi

What is the difference between light (photons) and electromagnetic waves (eg radio waves)?
According to some tables (like this ) the only difference is its wave length. But to me this doesen't make sense! i learned, that a photon just acts like a wave. furthermore a photon has got a mass (rest mass=0) , but i never heard this about em-waves.

Light behaves as a wave but also as a stream of incident particles. these particles are the photons. basically, a photon is a particle that corresponds to an energy-quantum : a little piece of EM-energy.

So both visions (photons <-->waves) are dual. Just compare it as using two different languages to say the same...

Indeed a photon has restmass = 0 and it always has velocity = c.

The EM-energy is quantized, which means it can only have certain values and such an energy-unit really is a photon.

http://en.wikipedia.org/wiki/Photon

Uh, and it would be possible to slow down the speed of light if it were a 'normal' em-wave, wouldn't it? Urks...

YES YOU CAN
http://physicsweb.org/articles/news/9/3/10/1

(though, i don't know whether you will understand everything in this article, it gives a good image of what is goin on)
regards
marlon

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Light is just one kind of electromagnetic wave. Wavelength and frequency vary inversely with one another to describe different types of EM waves. If you're using the word 'photon' to describe light, you can equally use it to describe X-rays, microwaves and radio waves, all of which belong to the electromagnetic spectrum.

A radio wave is exactly the same as a light wave, except that its frequency is a lot lower and its wavelength is a lot higher.

Thanks brewnog.

This means, the maxwell equations are valid for light-waves too; ok, that's not very surprising for me. But that an x-ray could be described as a photon stream is very interesting.

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brewnog said:
Light is just one kind of electromagnetic wave. Wavelength and frequency vary inversely with one another to describe different types of EM waves. If you're using the word 'photon' to describe light, you can equally use it to describe X-rays, microwaves and radio waves, all of which belong to the electromagnetic spectrum.

Just a terminological note here. In common usage, "light" usually means visible light, but in the astro literature I've seen, "light" can refer to electromagnetic radiation of any wavelength, including radio waves and x-rays. I don't know what the standards are in other fields. As for the difference between photons and classical waves, I think that was answered well by marlon.

## What is an electromagnetic wave?

An electromagnetic wave is a type of energy that is made up of oscillating electric and magnetic fields. It can travel through a vacuum and does not require a medium to travel through, unlike sound waves.

## How fast do electromagnetic waves travel?

Electromagnetic waves travel at the speed of light, which is approximately 299,792,458 meters per second in a vacuum.

## What is the difference between electromagnetic waves and light?

Light is a type of electromagnetic wave that is visible to the human eye. Electromagnetic waves also include forms of energy that are not visible, such as radio waves, microwaves, and x-rays.

## What are the properties of electromagnetic waves?

Electromagnetic waves have several key properties, including wavelength, frequency, amplitude, and speed. The wavelength is the distance between two consecutive peaks or troughs of the wave. The frequency is the number of waves that pass a point in one second. The amplitude is the height of the wave, and it determines the intensity or brightness of the wave. The speed of electromagnetic waves is constant in a vacuum and depends on the medium it is traveling through.

## How are electromagnetic waves used in everyday life?

Electromagnetic waves have a wide range of applications in our everyday lives. They are used in communication systems, such as radios, televisions, and cell phones. They are also used in medical imaging, such as x-rays and MRI scans. Other uses include cooking with microwaves, generating electricity with solar panels, and heating food with infrared radiation.

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