# Electromagnetic waves

## Homework Statement

I have to re-write the following statement because it is either incomplete or false. When an electromagnetic waves passes from one material into another with a higher index of refraction, its frequency will increase.

N/A

## The Attempt at a Solution

It sounds perfect already. I dont see anything incomplete about it. When the index of refraction goes up, so does its frequency.

---------------------------------------------------------------------------------

## Homework Statement

Visible light is usually seen in straight lines, while radio waves seem to be able to bend around houses and other similar sized objects. If they are both electromagnetic waves, why the apparent difference?

n/a

## The Attempt at a Solution

Does it have anything to do with light acting as both a particle and a wave?

Doc Al
Mentor

## Homework Statement

I have to re-write the following statement because it is either incomplete or false. When an electromagnetic waves passes from one material into another with a higher index of refraction, its frequency will increase.

N/A

## The Attempt at a Solution

It sounds perfect already. I dont see anything incomplete about it. When the index of refraction goes up, so does its frequency.
What makes you think this? Something changes when waves change media, but what? Look it up.

## Homework Statement

Visible light is usually seen in straight lines, while radio waves seem to be able to bend around houses and other similar sized objects. If they are both electromagnetic waves, why the apparent difference?

n/a

## The Attempt at a Solution

Does it have anything to do with light acting as both a particle and a wave?
No. Compare the length of the waves. What is this "bending around obstacles" called? (Look it up!)

I did look up the first one, in my notes and on google. Im getting the same thing.

O i get it. Since radio waves have a larger wavelength, the diffraction (bending of a wave) will also increase. Visible light has a smaller wavelenghth, so its diffraction isnt as great and cannot bend the walls.

Doc Al
Mentor
I did look up the first one, in my notes and on google. Im getting the same thing.
Are you saying you found physics sites that said that frequency of a wave increases when it passes into a medium of higher index of refraction? I hope not! (If so, give a reference and I'll check it out.)

O i get it. Since radio waves have a larger wavelength, the diffraction (bending of a wave) will also increase. Visible light has a smaller wavelenghth, so its diffraction isnt as great and cannot bend the walls.
Exactly.

K i was thinking of wrong thing for first one.

If index of refraction increases, then diffraction increases, which really means that wavelenght increases. Since wavelength increases, then frequency goes down?

Doc Al
Mentor
If index of refraction increases, then diffraction increases, which really means that wavelenght increases.
Nope.
Since wavelength increases, then frequency goes down?
How do you figure this?

Last edited by a moderator:
ok so its unchanged.

Thanks for help

Frequency of EM waves

Frequency of electromagnetic waves does not change when traveling through mediums of different index of refraction.
In fact, when a wave of frequency "f" in a medium of index "n1" passes to a medium of index "n2", the frequency of the wave does not change, but it is its wavelength that changes.

f = v1/λ1 = v2/λ2
where "vi" is the speed of light in medium i and "λi" is the wavelength of the electromagnetic wave.
and
vi = c/ni where "c" is the speed of light in free space and it equals 300,000,000m/s.

So we see that the speed of light in the medium and the wavelength change in a manner that the frequency remain constant.