Question

Ultraviolet light of wavelength 300 nm and intensity 1.0 Wm⁻² falls on the surface of a photosensitive material. If one percent of the incident photons produce photoelectrons, then the number of photoelectrons emitted from an area of 1.0 cm² of the surface is nearly ______.

Options

• 9.41 × 10¹⁴ s^-1

• 4.12 × 10¹³ s^-1

• 1.51 × 10¹² s^-2

• 2.13 × 10¹¹ s^-2

Answer 1

Ultraviolet light of wavelength 300 nm and intensity 1.0 Wm⁻² falls on the surface of a photosensitive material. If one percent of the incident photons produce photoelectrons, then the number of photoelectrons emitted from an area of 1.0 cm² of the surface is nearly 1.51 × 10¹² s^-2.

Explanation:

Energy incident over 1 cm² = 1.0 × 10⁻⁴J;

Energy of photon E = `"hc"/lambda`​

Total no of photons falling

= `(1.0xx10^-4)/("hc"/lambda)=(10^-4xx300xx10^-9)/(6.6xx10^-34xx3xx10^8)`

No of photoelectrons emitted per second

= `1/100xx(10^-4xx300xx10^-9)/(6.6xx10^-34xx3xx10^8)`

= 1.51 × 10¹²