A 17 mm wide diffraction grating has rulings of 530 lines per mm.Light is incident normally on the grating.The longest wavelength that forms an intensity maximum in the fifth order is closest to:
A)377 nm
B)352 nm
C)402 nm
D)427 nm
E)452 nm

Question

Quizplus · Accepted Answer

The longest wavelength that forms an intensity maximum in the fifth order is given by:$$\lambda = \frac{d \sin 	heta}{m}$$where d is the grating spacing, $	heta$ is the angle of diffraction, and m is the order of the maximum.For normal incidence, $	heta = 0$, so:$$\lambda = \frac{d}{m}$$Substituting the given values, we get:$$\lambda = \frac{17 	ext{ mm}}{530 	ext{ lines/mm} 	imes 5} = 377 	ext{ nm}$$Therefore, the correct choice is A.

A 17 Mm Wide Diffraction Grating Has Rulings of 530