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:$$\lambda = \frac{d}{5m}$$where d is the grating spacing and m is the order of the maximum.Substituting the given values, we get:$$\lambda = \frac{1}{890 	ext{ lines/mm} 	imes 5} = 225 	ext{ nm}$$Therefore, the correct choice is A.

A Diffraction Grating Has Rulings of 890 Lines/mm