The distance between the ruled lines on a diffraction grating is 1,770 nm.The grating is illuminated at normal incidence with a parallel beam of white light in the 400 nm to 700 nm wavelength band.What is the longest wavelength that appears in the third order spectrum?
A)590 nm
B)570 nm
C)550 nm
D)530 nm
E)610 nm

Question

Quizplus · Accepted Answer

The longest wavelength that appears in the third order spectrum can be found using the grating equation: d*sin(θ) = m*λ. For the third order (m=3), and maximum angle θ = 90 degrees, the longest wavelength λ = d/m = 1770 nm / 3 = 590 nm.

The Distance Between the Ruled Lines on a Diffraction Grating