Q. The electron in the hydrogen atom jumps from excited state (n = 3) to its ground state (n = 1) and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron in nth state En = −13.6/n² eV)
A) 5.1 V
B) 12.1 V
C) 17.2 V
D) 7 V
Explanation
[Solution from source] Photon energy for n = 3 → 1 is 13.6(1 − 1/9) = 12.09 eV. Maximum kinetic energy = 12.09 − 5.1 ≈ 7.0 eV, so the stopping potential is about 7 V. 12.1 V forgets to subtract the work function. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.