Diffraction grating: A diffraction grating has rulings of 890 lines/mm. When white light is incident normally on the grating, what is the longest wavelength that forms an intensity maximum in the fifth order?
A) 225 nm
B) 200 nm
C) 250 nm
D) 275 nm
E) 300 nm

Question

Quizplus · Accepted Answer

The longest wavelength that forms an intensity maximum in the fifth order is given by:$$\lambda = \frac{d}{m}$$where:* $\lambda$ is the wavelength* $d$ is the grating spacing* $m$ is the order of the maximumIn this case, $d = 1/890 	ext{ mm} = 1.124 	imes 10^{-3} 	ext{ mm}$ and $m = 5$. Therefore,$$\lambda = \frac{1.124 	imes 10^{-3} 	ext{ mm}}{5} = 224.8 	ext{ nm}$$which is closest to choice A, 225 nm.

Diffraction Grating: a Diffraction Grating Has Rulings of 890 Lines/mm