Ncert Exercises & Solutions

Two H atoms in the ground state collide inelastically. The maximum amount by which their combined kinetic energy is reduced is:

1. 10.20 eV

2. 20.40 eV

3. 13.6 eV

4. 27.2 eV

(1) Hint: The combined kinetic energy is reduced due to the excitation of any one of the H-atoms.

Step 1: Find the total energy of the H-atoms.

The total energy associated with the two H atoms in the ground state colliding elastically

= 2 \times (13.6 eV) = 27.2 eV

Step 2: Find the loss in kinetic energy.

The maximum amount of their combined kinetic energy is reduced when any one of them goes into first excited state after the inelastic collision.

The total energy associated with the two H-atoms after the collision

= (\frac{13.6}{2^{2}}) + (13.6) = 17.0 eV

Therefore, maximum loss of their combined kinetic energy = 27.2 - 17.0 = 10.2 eV