Chemistry - Atomic Structure Question with Solution | TestHub
Light of wavelength 400 nm (photon energy 3.1 eV) falls on four metals whose work functions are P: cesium, 1.9 eV; Q: sodium, 2.3 eV; R: zinc, 4.3 eV; S: calcium, 2.9 eV. Match each metal with the statements in Column II that are true for it (hc = 1240 eV nm) (a Column I entry may match more than one Column II entry):
Column I (Metal) | Column II (Statement) |
|---|---|
(P) cesium | (1) maximum K.E. of the photoelectrons is greater than 1 eV |
(Q) sodium | (2) photoelectrons are emitted |
(R) zinc | (3) threshold wavelength is greater than 500 nm |
(S) calcium | (4) stopping potential is 0.8 V |
| (5) no photoelectrons are emitted |
| (6) threshold wavelength lies between 400 nm and 500 nm |
Choose the option with the correct matching:
Options:
Answer:
Solution:
Threshold wavelength = 1240/φ: Cs 653 nm, Na 539 nm, Zn 288 nm, Ca 428 nm. K.E.max = 3.1 - φ: Cs 1.2 eV, Na 0.8 eV, Zn none, Ca 0.2 eV.
(P) 1, 2, 3.
(Q) K.E. 0.8 eV so stopping potential 0.8 V: 2, 3, 4.
(R) 3.1 eV < 4.3 eV, so no emission (5).
(S) Emission with 0.2 eV (2); threshold 428 nm lies between 400 and 500 nm (6).
Correct matching: P to 1,2,3; Q to 2,3,4; R to 5; S to 2,6. Answer: (D).
