1. Bohr frequency condition

When an electron transitions between two energy levels in a hydrogen atom, the energy difference is related to radiation by

$h f = |E_2 - E_1|$

More specifically:

• For absorption (electron goes from lower to higher energy level): $h f = E_2 - E_1$
• For emission (electron goes from higher to lower energy level): $h f = E_2 - E_1$ where $E_2 > E_1$.

So in both cases, the photon energy equals the positive energy difference between the two levels.

2. Check Statement I

Statement I says:

In hydrogen atom, the frequency of radiation emitted when an electron jumps from lower energy orbit $(E_1)$ to higher energy orbit $(E_2)$, is given as $hf = E_1 - E_2$.

This is incorrect for two reasons:

• Going from lower to higher energy orbit is absorption, not emission.
• The correct relation should be $h f = E_2 - E_1$ not $E_1 - E_2$.

Therefore, Statement I is false.

3. Check Statement II

Statement II says:

The jumping of electron from higher energy orbit $(E_2)$ to lower energy orbit $(E_1)$ is associated with frequency of radiation given as $f = \frac{E_2 - E_1}{h}$ This condition is Bohr's frequency condition.

For a transition from higher level to lower level, radiation is emitted and

$h f = E_2 - E_1$

Hence,

$f = \frac{E_2 - E_1}{h}$

This is correct.

Therefore, Statement II is true.

4. Conclusion

• Statement I: Incorrect
• Statement II: True

Hence the correct option is:

$\boxed{\text{D}}$