A 5 watt source emits monochromatic light of wavelength 5000Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.. m, the number of photoelectrons liberated will be reduced by a factor of

Options

(a) 8
(b) 16
(c) 2
(d) 4

Correct Answer:

4

Explanation:

No. of emitted electrons Nₑ ∞ Intensity ∞ 1 / (distance)²
Therefore, as distance is doubled, Nₑ decreases by (1/4) times.