1
43kviews
A diffraction grating have 4000 lines per cm is illuminated normally by light of wavelength 5000 ˚A. Calculate its dispersive power in third order spectrum.
1 Answer
3
9.2kviews

N = 4000 line/cm, λ = 5000 x108, n= 3

\frac{dθ}{dλ}= \frac{n}{(a+b)cosθ} \\[3ex] (a+b) sinθ = nλ \\[2ex] sinθ = \frac{nλ}{(a+b)} \\[2ex] sinθ = N nλ \,\,\,\,\,\ [\because (a+b) = \frac{1}{N}] \\[2ex] sinθ = 4000 \times 3 \times 5000 \times 10^{-8} = 0.6 \\[2ex] θ= 36.86

cosθ = …

Create a free account to keep reading this post.

and 5 others joined a min ago.

Please log in to add an answer.