Concepts Of Physics MCQ Edition [Volume 2]PhysicsPhotoelectric Effect and Wave–Particle Duality
A metal plate with a work function of 2.2 eV is illuminated by a light beam having a wavelength of 400 nm . A particular electron absorbs a photon and undergoes two collisions before emerging from the metal. Assuming that 10 % of the extra energy is lost to the metal during each collision, determine the kinetic energy of this electron as it exits the metal.
Options
- A0.31 eV
- B0.59 eV
- C0.73 eV
- D0.90 eV
Correct answer
A. 0.31 eV
Step-by-step solution
Energy of the incident photon is given by: E = hc Using hc = 1240 eV nm and = 400 nm : E = 1240 400 = 3.1 eV The electron absorbs this photon, so its extra energy inside the metal is 3.1 eV . During each collision, the electron loses 10 % of its extra energy to the metal, meaning it retains 90 % of its energy after each collision. Energy remaining after two collisions is: E' = 3.1 (0.9)^2 = 3.1 0.81 = 2.511 eV To emerge from the metal, the electron must overcome the work function = 2.2 eV . The kinetic energy of th