Question 233: Dual Nature of Matter and Radiation

Question

A certain metallic surface is illuminated by monochromatic radiation of wavelength $$\lambda$$. The stopping potential for photoelectric current for this radiation is 3V
0
. If the same surface is illuminated with a radiation of wavelength 2$$\lambda$$, the stopping potential is V
0
. The threshold wavelength of this surface for photoelectric effect is ____________ $$\lambda$$.

Accepted Answer

$$KE = {{hc} \over \lambda } - \phi hc$$
$$e(3{V_0}) = {{hc} \over \lambda } - \phi $$ ..... (i)
$$e{V_0} = {{hc} \over {2\lambda }} - \phi $$ ..... (ii)
Using (i) & (ii)
$$\phi  = {{hc} \over {4{\lambda _0}}} = {{hc} \over {{\lambda _t}}}$$
$${\lambda _t} = 4{\lambda _0}$$

Dual Nature of Matter and Radiation

Integer / Numeric Answer Type