Question

 A parallel beam of red light of wavelength 650nm arrives normally at a diffraction grating. The first order maximum has an angle of 40°. Calculate the total number of principal maxima this grating can produce for the red light. At what angle is the highest order maxima produced?

Answer 1

Answer

Relationship is given

the total number of principal maxima this grating can produce for the red light.

$N=\frac{sin\theta}{n\lambda}\\=\frac{sin40^°}{1\times650\times10^{-9}}\\=989\times10^{3}$

Now

At what angle is the highest order maxima produced is $\theta=90^°$