Browse Questions

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

$\begin {array} {1 1} (a)\;1W\: IR\: lamp & \quad (b)\;50\: W\: UV\: lamp \\ (c)\;50\: W \: IR \: lamp & \quad (d)\;10 \: W\: IR\: lamp \end {array}$

Ans : (b)
For photoelectric emission to take place the wavelength of incident
light must be less than
threshold value which is 5200 $A^{\circ}$
wavelength of IR light = 7800 $A^{\circ}$
wavelength of UV light = 4000 $A^{\circ}$

edited Mar 13, 2014