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# I can't solve this question watch

1. Assume that the two light waves, of wavelength 510 nm in air, are initially out of phase by π rad. The indexes of refraction of the media are n1 = 1.46 and n2 = 1.73. What are the
(a) smallest and (b) second smallest value of L that will put the waves exactly in
phase once they pass through the two media?

https://postimg.org/image/4t4eluioh/

I literally don't know what to work out help please
2. (Original post by Aydawg)
Assume that the two light waves, of wavelength 510 nm in air, are initially out of phase by π rad. The indexes of refraction of the media are n1 = 1.46 and n2 = 1.73. What are the
(a) smallest and (b) second smallest value of L that will put the waves exactly in
phase once they pass through the two media?

https://postimg.org/image/4t4eluioh/

I literally don't know what to work out help please
We'll start with (a) so you can get the idea for (b).

How many wavelengths can you have in a distance L through the two refractive media? How many radians does this correspond to?

If you want them to be in phase when they leave the media, what is the condition on the difference in radians of the two waves (given that they come in pi radians out of phase)?

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Updated: January 30, 2017
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