Question

Threshold wavelength for photoelectric emission from a metal surface is 5200 $A^0$. Photoelectrons will be emitted when this surface is illuminated with monochromatic radiation from

• A. 50W UV lamp
• B. 1W I R Lamp
• C. 10W IR Lamp
• D. 50W IR lamp

Answer 1

The correct option is A

50W UV lamp

${\lambda }_0=5200\times {10}^{-10}m$

Photo electrons will be emitted if the incident radiations has a wavelength less than ${\lambda }_0$

$\therefore$ UV lamp emits radiation of wavelength less than $5200\times {10}^{-10}m$