Silver has a work function of 4.7 eV. When ultraviolet light of wavelength 100 mm is incident upon it, a potential of 7.7 V is required to stop the photoelectrons from reaching the collector plate. How much potential will be required to stop the photoelectrons when light of wavelength 200mm is incident upon silver?

Options

A. 1.5 V
B. 3.85 V
C. 2.35 V
D. 15.4 V

Answer

A

Explanation

`lamda=(12375)/(E_1(eV))A=1000A`
`E_1=12.375eV`
Similarly, `(12375)/(lamda_2(A))eV=(12375)/(2000)=6.1875 eV`
Now, `E_1W_0=eV_S`
and `E_2-W_0=eV_S`
Hence, `12.375-W_0=7.7eV`
and `6.1875-W_0=eV_s^``
Solving, we get `V_s^`=1.5 V`