Sunlight is incident on a diffraction grating that has 3,550
lines/cm. The second-order spectrum over the visible range (400-700
nm) is to be limited to 2.05 cm along a screen that is a distance
L from the grating. What is the required value of
L?
U
The distance between the lines in meteris
d = 1cm / 3550 =10-2 m / 3550
=2.8169*10-6 m
using the formula
d Sin θ = m λ
θred = Sin-1 ( 2λred / d ) = sin-1[ 2*700nm / d]
=22.65o
θviolet = 12.71o
The required value of L is
L = Δ y / [ tanθred -tanθviolet ]
= 2.05 cm / [ tan22.65 - tan12.71]
=10.69 cm.
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