### NEET Solved Paper 2017 Question 5

##### Question: The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m, is

#### Options:

A) $ \frac{2h}{\sqrt{mkT}} $

B) $ \frac{h}{\sqrt{mkT}} $

C) $ \frac{h}{\sqrt{3mkT}} $

D) $ \frac{2h}{\sqrt{3mkT}} $

## Show Answer

#### Answer:

Correct Answer: C

#### Solution:

- de-Broglie wavelength $ \lambda =\frac{h}{mv} $ $ =\frac{h}{\sqrt{2m(KE)}} $ $ =\frac{h}{\sqrt{2m(\frac{3}{2}kT)}} $ $ \lambda =\frac{h}{\sqrt{3mkT}} $