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How many orders will be observed by grating having 4000 lines/cm, if it is illuminated by light of wavelength in the range 5000 to 7500 $\mathring{A}$?
written 7.9 years ago by gravatar for neeta.vanage neeta.vanage • 880 modified 3.9 years ago by gravatar for pedsangini276 pedsangini276 • 4.8k

Subject: Applied Physics 2

Topic: Interference And Diffraction

Difficulty: Medium
engineering physics
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written 7.8 years ago by gravatar for neeta.vanage neeta.vanage • 880

Grating equation is (a+b) sinθ =nλ , N= 4000 lines/cm

For maximum orders sinθ = 1

Therefore , $ n_{max} = \frac{(a+b)}{λ} = \frac{1}{Nλ} $

For 5000 Å, $ n_{max} = \frac{1}{4000 \times 5000 \times 10^{-8}} = 5.$

For 7500 Å, $ n_{max} = \frac{1}{4000 \times 7500 \times 10^{-8}} = …

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