# Finding the frequency and wavelength of an electromagnetic wave

1. Jul 8, 2013

### aChordate

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Do I set up a proportion to first find the frequency of the electromagnetic wave in glass?

1.33/(3.42*1014)=1.62/fglass= 4.17*1014

2. Jul 8, 2013

### Dick

Put the equations aside for a minute and imagine your wave propagating from water into glass. Can the frequency change?

3. Jul 8, 2013

### aChordate

I was wondering about that. I wouldn't think the frequency or the wavelength would change. Maybe it would just be slowed down??

4. Jul 8, 2013

### Dick

Pick a point in the water and imagine you have 100 waves/sec passing by. Now pick a point in the glass. You must also have 100 waves/sec passing by, otherwise some waves are getting lost somewhere in between. Can't happen. Now tell me again what can change.

5. Jul 8, 2013

### aChordate

So the frequency changes, but not the wavelength?

6. Jul 8, 2013

### Dick

That's sort of the opposite of what I was trying to convey. If 100 waves/sec go in one end then 100 waves/sec must come out the other end, otherwise something is eating waves in between. That's not the picture. I'm trying to convince you the frequency can't change. So two other things must change.

7. Jul 8, 2013

### aChordate

Wavelength and velocity.

Glass would decrease the velocity and also decrease the wavelength (?)

8. Jul 8, 2013

Sure!