Hi

A liitle help will be appreciated. The question is as follows:

A laser beam of wavelength 630nm is directed normally at a diffraction grating with 300 lines per millimetre. Calculate:

a) The angle of diffraction of each of the first 2 orders

b) The number of diffracted orders produced

Solution

I used the formula

d X sintheta = n x wavelength

N= 300000

therefore d= 1/300000

n=2

Wavelength = 630nm

Putting the above value in I obtained 22 .2 degrees

b) For the second part, I surmised that theta = 90 degrees

Therefore,

n = d/wavelength

I obtained 5. 29. But this diifers from the books answer.

Please help!