First slide

Photoelectric effect and study of photoelectric effect

Question

Ultraviolet light of wavelength 300 nm and intensity 1.0 W m^-2 falls on the surface of a photosensitive material. If one per cent of the incident photons produce photoelectrons, then the number of photoelectrons emitted per second from an area of 1.0 cm² of the surface is nearly

Moderate

A

$9.61 \times 10^{14} s^{- 1}$
B

$4.12 \times 10^{13} s^{- 1}$
C

$1.51 \times 10^{12} s^{- 1}$
D

$2.13 \times 10^{11} s^{- 1}$

Solution

$\begin{array}{l} n = \frac{power}{h c / λ} = \frac{300 \times 10^{- 9}}{6.6 \times 10^{- 34} \times 3 \times 10^{8}} \\ = 1.5 \times 10^{18} m^{- 2} s^{- 1} = 1.5 \times 10^{14} s^{- 1} \end{array}$
As only 1 percent of photons cause emission of photoelectrons, number of photo electrons is $n_{e} = 1.5 \times 10^{12} s^{- 1}$

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