The angular separation between principal maxima for a grating consisting of 10,000 slits is 30º. The approximate angular width of the principal maxima is
A) .003º.
B) .3º.
C) 30º.
D) Hold it! The angle is much greater than 360º.

Question

Quizplus · Accepted Answer

The angular width of the principal maxima for a diffraction grating is given by the formula Δθ = λ/d, where λ is the wavelength of light and d is the grating spacing. The angular separation between principal maxima is related to the number of slits (N) and the grating spacing, but the width of each maximum is inversely proportional to the number of slits. Given a large number of slits (10,000 in this case), the width of each maximum will be very small, much smaller than the angular separation between them. Therefore, the correct answer is the smallest value given, which is .003º, indicating a very narrow principal maximum.

The Angular Separation Between Principal Maxima for a Grating Consisting