A monochromatic light source of intensity mW emits $$8\times10^{15}$$ photons per second. This light ejects photoelectrons from a metal surface. The stopping potential for this setup is $$2.0V$$. Calculate the work function of the metal.
Correct option is A. 2
(Given $$V_0=2V$$, No of photons = $$8\times10^{15}$$, Power = $$5mW$$)
The work function of material is given as:
$$W_0=h\nu-eV_0$$
$$=\dfrac { 5\times { 10 }^{ -3 } }{ 8\times { 10 }^{ 15 } } -1.6\times { 10 }^{ -19 }\times$$ $$ 2$$
$$=6.25\times { 10 }^{ -19 }-3.2\times 10^{ -19 }=3.05\times 10^{ -19 }J$$
$$=\dfrac { 3.05\times { 10 }^{ -19 } }{ 1.6\times { 10 }^{ -19 } } =1.906eV.$$