The first -order reflection of a beam of X-ray from (200) face of NaCl occurs at an angle `6^(@)30,(d_(200)=a)`, what is the wavelength of X-ray used `(A^(@))` where `d=((a)/sqrt(h^(2)+k^(2)+1^(2)))`.

Options

A. 0.6
B. 1.6
C. 2.8
D. 3.4

Explanation

`nlambda=2d sin theta` (n=1)
NaCl has fcc lattice
So, `d_(200)=(alpha)/(2)rArr lambda=2xx(alpha)/(2)sin theta`
`rArr lambda=alpha sin theta,rArrtheta,rArrtheta=6^(@)30`.
So,
`lambda=alpha sin (6^(@)30')=5.64xx0.113=0.637overset(@)A`.