Number of diffracted orders produced

[aurao2003]

Homework Statement

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

Homework Equations

I used the formula

d X sintheta = n x wavelength

The Attempt at a Solution

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!

 

[Stonebridge]

I've replied to this on TSR.

 

[aurao2003]

lol! Apologies again. You could probably guess I post on a few forums. Please keep on tracking me. Its highly appreciated.