Ultraviolet light of wavelength `800 A` and `700 A` when allowed to fall on hydrogen atoms in their ground states is found to liberate electrons with kinetic energies `1.8eV` and `4.0eV`, respectively. Find the value of Planck's constant.

Explanation

To find the value of Planck's constant (h) using the given data, we can follow these steps:

### Step 1: Understand the Photoelectric Effect Equation
The energy of the incident light can be expressed using the equation:
\[ E = K.E + W \]
where:
- \( E \) is the energy of the incident photon,
- \( K.E \) is the kinetic energy of the emitted electron,
...