The largest distance between the interatomic planes of crystal is `10^(-7) cm`. The upper limit for the wavelength of `X` - rays which can be usefully studied with this crystal is

Options

A. `1 Å`
B. `2 Å`
C. `10 Å`
D. `20 Å`

Answer

D

Explanation

Bragg's law , `2d sin theta = n lambda or lambda = ( 2d sin theta)/(n)`
For maximum wavelength , `n_(min) = 1 , (sin theta )_(max) = 1`
`:. Lambda_(max) = 2d or lambda_(max) = 2 xx 10^(-7) cm = 20 Å``