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The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of incident radiation for which the stopping potential is 5 V lies in the:

1. Ultraviolet region
2. Visible region
3. Infrared region
4. X-ray region

Correct answer: Ultraviolet region

Solution

The stopping potential of 5 V corresponds to a photon energy of 5 eV. Adding the work function (6.2 eV), the total photon energy is 11.2 eV. Using E = hc/λ, this corresponds to a wavelength in the ultraviolet region.

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