## anonymous one year ago If a beam of light from a He-Ne laser has wavelength 543 nm in air, what is its wavelength in water? The index of refraction for water is 1.33. 722 nm , 408 nm , 540 nm , or 360 nm ?

1. Michele_Laino

the light speed v in water is: $v = \frac{c}{n}$

2. Michele_Laino

n is the refractive index of water

3. anonymous

ok! what can we plug in? :/

4. Michele_Laino

we can write this: ${\lambda _2}\nu = \frac{{{\lambda _1}\nu }}{n}$

5. Michele_Laino

since the frequency is the same inside those two mediums, then we have: $\Large {\lambda _2} = \frac{{{\lambda _1}}}{n}$ where \lambda_1=543 nm, and \lambda_2 is the requested wavelength

6. anonymous

okay! so we plug in 543/n? what is n?

7. Michele_Laino

n=1.33

8. anonymous

so we get 408? 408 nm is our solution?

9. Michele_Laino

$\Large {\lambda _2} = \frac{{{\lambda _1}}}{n} = \frac{{543}}{{1.33}} = ...$

10. Michele_Laino

yes! That's right!

11. anonymous

yay!! thank you:)

12. Michele_Laino

:)