Fixing Light Issues in CD Readers

[nokia8650]

Hi

I am struggling with the problem below:

http://img134.imageshack.us/img134/8977/03jan.th.jpg [Broken]

I can do the first part, but don't know how to start the second part.

Thanks

 

[RoryP]

have you tried thinking about the conditions necessary for interference?? that might help =]

 

[Chewy0087]

^ - destructive interference especially