Question

What's the angle when the wavelength your looking at is 400 nm and the spacing grating is 2000 nm

Answer 1

using diffraction equation

where n is the order of diffraction

is the wavelength

d is the spacing between grooves of a grating

substitute the given value in the above formula

n * 400 * 10-9 = 2000*10-9*Sin

n=5 Sin

therefore for different values of n , we have different angles of diffraction

for n = 1 , = 11.54 degree

for n = 2 , = 23.58 degree

for n = 3 , = 36. degree

for n = 4 , = 53.1 degree

and so on....

most prominently we see at the first order of diffraction, therefore angle = 11.54 degree.