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 $\mathring{A}$?

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written 6.9 years ago by

neeta.vanage • 870

modified 2.8 years ago by

pedsangini276 • 4.8k

Subject: Applied Physics 2

Topic: Interference And Diffraction

Difficulty: Medium

engineering physics

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1 Answer

6.6kviews

written 6.8 years ago by

neeta.vanage • 870

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}} = 3 $

So, in the wavelength range, 5000 to 7500 Å ,the observed number of orders range between 3 to 5

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