Dual Nature Of Light Question 99
Question: The largest distance between the interatomic planes of a crystal is 10-7cm. The upper limit for the wavelength of X-rays which can be usefully studied with this crystal is [CPMT 1984]
Options:
A) 1 Å
B) 2 Å
C) 10 Å
D) 20 Å
Show Answer
Answer:
Correct Answer: D
Solution:
Bragg’s law, $ 2d\sin \theta =n\lambda $ or $ \lambda =\frac{2d\sin \theta }{n} $
For maximum wavelength, $ {n_{\min }}=1,{{(\sin \theta )}_{\max }}=1 $
$ \therefore {\lambda_{\max }}=2d $ or $ {\lambda_{\max }}=2\times {{10}^{-7}}cm=20,{\AA} $
BETA
