A) 2.5
B) \[5.6\times {{10}^{-10}}\]
C) \[4\times {{10}^{-10}}\]
D) \[4.6\times {{10}^{-10}}\]
Correct Answer: B
Solution :
| Key Idea: From Braggs law, the condition for the reflection of X-rays from series of atomic layers in a given plane is, |
| \[2d\,\sin \theta =n\lambda \] |
| From key idea, |
| Wavelength \[\lambda =\frac{2d\,\sin \theta }{n}\] |
| \[{{\lambda }_{\max }}=\frac{2\,d\,{{(\sin \,\theta )}_{\max }}}{n}\] |
| \[=\frac{2\,d\times 1}{1}\] \[[\because \,\,{{(\sin \theta )}_{\max }}=1]\] |
| \[=2d\] |
| \[=2\times 2.8\times {{10}^{-10}}\,m\] |
| \[=5.6\times {{10}^{-10}}\,m\] |
| Note: Braggs reflection can occur only for wavelength \[\lambda \le 2d\]. Due to this fact, the visible light wavelength cannot be used in diffraction. |
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