Directions: are based on the following paragraph. |
Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure). |
Electrons accelerated by potential V are diffracted from a crystal. If \[d=1\overset{o}{\mathop{A}}\,\] and \[i={{30}^{o}}\], V should be about (\[h=6.6\times {{10}^{-34}}Js\],\[{{m}_{e}}=9.1\times {{10}^{-31}}kg,\,e=1.6\times {{10}^{-19}}C\]) [AIEEE 2008] |
A) 500 V
B) 1000 V
C) 2000 V
D) 50 V
Correct Answer: D
Solution :
[d] For constructive interference, path difference |
From the given figure, path difference = MP+PN = 2d cos i |
Also |
For n = 1, V = 50 volt |
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