Suggest one reason why the fringe pattern produced by light passing through a
diffraction grating is brighter than that produced from the same source with a double slit

Question

Suggest one reason why the fringe pattern produced by light passing through a
diffraction grating is brighter than that produced from the same source with a double slit

samgrace · Answer

The angular width of the interference maximum, which is equal to 2 * theta_mins, is inversely proportional to N. Therefore the greater the number of illuminate slits N, the sharper the maximum. 

Diffracton grating: $$Nd \sin \theta = \lambda $$

where N is the number of slits

anonymous · Answer

Isn't N the order of the diffracted beam? @samgrace

samgrace · Answer

No

samgrace · Answer

dsin(theta) = m*lamda , where m = 1, 2 ,3 , m is the order of diffration

anonymous · Answer

Okay, N is the number of slits, right. 
So the distance between slits and number of slits is related by d=1/N

anonymous · Answer

If N is greater, d decreases.

samgrace · Answer

Yeah

anonymous · Answer

And thus if d decreases, the order (m) also decreases. So, the lights is less spread out and brighter?

samgrace · Answer

The first and the last slits are separated by approximately N*d, so the intensity will be zero at angle theta_min, I think correct.