# Homework Help: Wavelenght, index of refraction and speed

1. Feb 16, 2010

### dev-hud

THe wavelength of a red helium-neon laser light in air is 632.8 nm.

A) what is the frequency? ( i already figured this out to be 4.7 x 10^16)

B) what is its wavelenght in glass that has an index of refraction of 1.50?( i do not know where to or if i have to plug in the refraction into an equation and if i do what equation do i use?)

C) what is its speed in the glass? ( is this then related to question B? because i do not know how now to bring in v into the equation and what the equation is. i am just confuzed)

2. Feb 16, 2010

### tramar

$$n=\frac{\lambda_0}{\lambda}$$

$$\lambda_0$$ is the wavelength in air.

Part c should be easy once you have part b.

3. Feb 16, 2010

### collinsmark

Btw, you might want to double check that. If your units are Hz, I think you are a couple orders of magnitude off.

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