Q14.A metal surface is illuminated by a radiation of wavelength 4500 A . The ejected photo-electron enters a constant magnetic field of 2 mT making an angle of 90° with the magnetic field. If it starts revolving in a circular path of radius 2 mm, the work function of the metal is approximately (1) 1. 36 eV (2) 1. 69 eV (3) 2. 78 eV (4) 2. 23 eV
What This Question Tests
This multi-concept question combines the photoelectric effect to find the kinetic energy of emitted electrons with the motion of a charged particle in a magnetic field to find its speed and then the work function.
Concepts Tested
Formulas Used
KE_max = hν - φ_0 = hc/λ - φ_0
F_magnetic = qvB
Centripetal force = mv²/r
1 eV = 1.6 × 10⁻¹⁹ J
📚 NCERT Sections This Tests
11.2 — The Work Function Of Caesium Metal Is 2.14 Ev. When Light Of
Physics Class 12 · Chapter 11
11.2 The work function of caesium metal is 2.14 eV. When light of frequency 6 ×1014Hz is incident on the metal surface, photoemission of electrons occurs. What is the (a) maximum kinetic energy of the emitted electrons, (b) Stopping potential, and (c) maximum speed of the emitted photoelectrons?
11.7 — The Work Function For A Certain Metal Is 4.2 Ev. Will This Metal Give
Physics Class 12 · Chapter 11
11.7 The work function for a certain metal is 4.2 eV. Will this metal give hotoelectric emission for incident radiation of wavelength 330 nm?
11.6 — The Threshold Frequency For A Certain Metal Is 3.3 × 1014 Hz. If Light
Physics Class 12 · Chapter 11
11.6 The threshold frequency for a certain metal is 3.3 × 1014 Hz. If light of frequency 8.2 × 1014 Hz is incident on the metal, predict the cut- off voltage for the photoelectric emission.
📋 Question Details
- Chapter
- Dual Nature of Matter
- Topic
- Photoelectric effect and magnetic force
- Year
- 2022
- Shift
- 26 Jun Shift 2
- Q Number
- Q14
- Type
- Multi concept
- NCERT Ref
- Class 12 Physics Ch 11: Dual Nature of Radiation and Matter
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