A 40 W ultraviolet light source of wavelength `2480 A`. Illuminates a magnesium (mg) surface placed 2 m away. Determine the number of photons emitted from the surface per second and the number incident on unit area of Mg surface per second . The photoelectric work function for Mg is `3.68eV`. Calculate the kinetic energy of the fastest electrons ejected from the surface. Determine the maximum wavelength for which the photoelectric effects can be observed with Mg surface.

Explanation

To solve the problem step by step, we will break down the calculations as follows:

### Given Data:
- Power of the ultraviolet light source, \( P = 40 \, \text{W} \)
- Wavelength of the light, \( \lambda = 2480 \, \text{Å} = 2480 \times 10^{-10} \, \text{m} \)
- Work function of magnesium, \( \phi = 3.68 \, \text{eV} \)

### Step 1: Calculate the Energy of a Single Photon
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