Wave property of electron implies that they will show diffraction effected . Davisson and Germer demonstrated this by diffracting electron from crystals . The law governing the diffraction from a crystals is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructiely as shown in figure
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A strong diffraction peak is obsrved,when electrons incident at an angle i from the normal to the crystal planes with distance d between them and as shown in the figure given above.de-Broglie wave length `lambda)` of electrons can be calculated by the relation (n is an integer)

Options

A. `d cos i =nlambda`
B. `d sin i = n lambda`
C. `2 d cos i = n lambda`
D. `2 d sin i = n lambda`.