# Indices of refraction when wavelengths are given

1. Jan 9, 2006

### oooo

A parallel beam of light containing two wavelengths, 1 = 400 nm and 2 = 650 nm, enters the silicate flint glass of an equilateral prism with an angle of incidence of 49 degrees. At what angle, relative to the normal, does each beam leave the prism?

This seems simple, but previously, I had solved somilar problems when the indices of refraction were given. So, I checked my textbook and it said that to find the indices of refraction use the formula lambda o/ lambda n. So I tried this and divided 589 nm (isn't this the speed of sound in a vacuum??) by 400 nm to get 1.4725. However, I noticed that for the second ray, the index ( 589 nm/ 650 nm) results in a number that is less than one. This cannot be right. Please help me find the indices of refraction so I can continue with this problem!
Thanks

2. Jan 9, 2006

### oooo

never mind

Never mind, you do not need to help me with this... my teacher just posted the indices on our website now... Thanks anyway!