Question

A copper ball of radius 1 cm work function 4.47 eV is irradiated with ultraviolet radiation of wavelength $2500\mathring{A}$. The effect of irradiation results in the emission of electrons from the ball. Further the ball will acquire charge and due to this there will be finite value of the potential on the ball. The charge acquired by the ball is :

• A. $5.5\times {10}^{-13}C$
• B. $7.5\times {10}^{-13}C$
• C. $4.5\times {10}^{-12}C$
• D. $2.5\times {10}^{-11}C$

Answer 1

The correct option is A $5.5\times {10}^{-13}C$

From photo electric effect equation :

]

$h\nu =h{\nu }_0+K.E_{max}$

so Maximum kinetic energy will be

$K.E_{max}=\frac{hc}{\lambda }-h{\nu }_0$

putting the given values in the above equation

$K.E_{max}=e\times V$

so V will be

$V=\frac{k\times Q}{r}$

:: $q=5.5\times {10}^{-13}C$