An electron having energy `20 e V` collides with a hydrogen atom in the ground state. As a result of the colllision , the atom is excite to a higher energy state and the electron is scattered with reduced velocity. The atom subsequentily returns to its ground state with emission of rediation of wavelength `1.216 xx 10^(-7) m`. Find the velocity of the scattered electron.

Explanation

To find the velocity of the scattered electron after it collides with a hydrogen atom in the ground state, we can follow these steps:

### Step 1: Calculate the energy of the emitted photon
The energy of the emitted photon can be calculated using the formula:
\[ E = \frac{hc}{\lambda} \]
where:
...