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Question:

For Bragg's diffraction by a crystal to occur, then the X-ray of wavelength λ and interatomic distance d must be?

λ is greater than 2d

λ equals 2d

λ is smaller than or equal to 2d

λ is smaller than 2d

Solution:

Correct option is C. λ is smaller than or equal to 2d
Bragg's law for diffraction by a crystal to occur: nλ = 2d sinθ
For n = 1
Since sinθ ≤ 1
For diffraction by crystal to occur λ is smaller than or equal to 2d