PYQ NEET- Photoelectric Effects Facts And Prospects

• (2017) A monochromatic light is incident on a metal surface. The graph of the stopping potential V versus the frequency v of the incident light is as shown. The threshold frequency of the metal is:

(A) 1 eV (B) 3 eV (C) 4 eV (D) 6 eV

• The answer is (C)

• The threshold frequency is the frequency of the incident light at which the stopping potential becomes zero. In this case, the stopping potential is zero when the frequency of the incident light is 4 eV.

• (2016) A photon of energy 10 eV is incident on a metal surface whose work function is 6 eV. The maximum speed of the photoelectrons emitted from the surface is:

(A) 10^5 m/s (B) 10^6 m/s (C) 10^7 m/s (D) 10^8 m/s

• The answer is (B)

• The maximum kinetic energy of the photoelectrons is equal to the energy of the incident photon minus the work function