Question
Question: Stopping potentials of 24, 100, 110, 115 kV are measured for photoelectrons emitted from a certain e...
Stopping potentials of 24, 100, 110, 115 kV are measured for photoelectrons emitted from a certain element when it is irradiated with monochromatic X-rays. The element is used as a target in an X-ray tube. The energy of Kα line is–
A
54 KeV
B
76 KeV
C
88 KeV
D
32 KeV
Answer
76 KeV
Explanation
Solution
Let EK, EL, EM, EN be the binding energies of K, L, M and N shell. Let EP be energy of incident photon. Then
EP – EK = 24 KeV ... (1)
EP – EL = 100 KeV ... (2)
EP – EM = 110 KeV .... (3)
E(Kα) = EK – EL = 100 – 24 = 76 KeV