# Angular spread of light rays passing through a prism

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1. Apr 18, 2017

### Quenton Robertson

1. The problem statement, all variables and given/known data
The index of refraction for violet light in silica flint glass is 1.66, and the index of refraction for red light is 1.62. What is the angular spread of visible light passing through a prism of apex angle 60 degrees if the angle of incidence is 50.03 degrees?

2. Relevant equations
n1=1.62
n2=1.66
n =1
theta1=50.03

3. The attempt at a solution
I plugged in my numbers into the equation above and got:

and got: 0.7388

but that was wrong...so where did I go wrong?

2. Apr 18, 2017

### BvU

0.7388 radians seems a bit much... Maybe you mean degrees ? Is that for the entrance into the glass only ?

3. Apr 18, 2017

### Quenton Robertson

yeah sorry, i meant degrees :P the question wants the answers in degrees too
is the 60 degree number important? if so where do i use it?

4. Apr 18, 2017

### BvU

You might use it on the other side of the prism to calculate the angle of incidence there...

Thing to do: make a drawing indicating the various angles...

5. Apr 18, 2017

### Quenton Robertson

Could you show me what you mean by that?

6. Apr 19, 2017

### Ibix

@Quenton Robertson - this is, I think, the key point.

7. Apr 19, 2017

### BvU

Maybe QR missed my second line in #4 (I first posted a one-liner )