Dual Nature of Radiation and Matter

The interplanar distance in a crystal is 2.8 10-8 m. The value of maximum wavelength which can be diffracted is

1. 2.8 10-8 m
2. 5.6 10-8 m
3. 1.4 10-8 m
4. 7.6 10-8 m

Answer

(2) 5.6 10-8 m

Solution

Bragg's law: 2d = n

is maximum when = 1 and n = 1:

⇒ max = 2d

= 2 2.8 10-8 m

= 5.6 10-8 m

Answer: (2)