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Question:

(a) Monochromatic light of frequency 6.0 × 10¹⁴ Hz is produced by a laser. The power emitted is 2.0 × 10⁻⁷ W. Estimate the number of photons emitted per second on an average by the source. (b) Draw a plot showing the variation of photoelectric current versus the intensity of incident radiation on a given photosensitive surface.

Solution:

(A). power = Energy/sec = nhv/sec
n/sec. = power/hv = 2 × 10⁻⁷ /6.0 × 10¹⁴ × 6 × 10⁻³⁴ = 5 × 10¹⁵
(B).