1, A grating with a groove density g = 1200 / mm is incorporated in a monochroma
ID: 1775305 • Letter: 1
Question
1, A grating with a groove density g = 1200 / mm is incorporated in a monochromator with 1. m focal length. Let the angle of incidence be 30 a) what would be the angle of diffraction for red light ( 650 nm) in first order? b) What is the angular dispersion d/dp at this wavelength? c) What mechanical slit width is required for a bandpass of 3 nm at this wavelength? 2. What are the main differences in the mechanism of light production between a regular light bulb and a LED? 3. What are the main differences in the mechanism of light detection between a photomultipli- er and a photodiode?Explanation / Answer
Ans:- Here g = 1200/mm
F=1m, lemda= 650nm, incident angle = 30deg, m= 1
1a. The general form of the grating equation is
m = d(sin i + sin r)
g = 1/d
d= 1/g = 1/ 1200 = 8.33*10^-4mm
650*10^-9 = 8.33*10^-7(sin30+ sin)
Sin =0.7803
=51.29deg
b] d/d=dcos/m = 8.33*10^-7*cos51.29/1 =5.2*10^-7m
c]bandpass = slit width * reciprocal of linear dispersion
B=w*P
P= focal length* angular dispersion = 1* 5.2*10^-7 =5.2*10^-7m
3*10^-9 = w*5.2*10^-7
W = 5.77*10^-3m
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