JEE Main 2020 · PhysicsNumerical answerNumerical valueMediumMulti-step

JEE Main 2 September 2020, Shift 1, Physics Q25

Question 25 of 75 in this shift, Physics question 25 of 25.

When radiation of wavelength

\lambda

is used to illuminate a metallic surface, the stopping potential is

V

. When the same surface is illuminated with radiation of wavelength

3\lambda

, the stopping potential is

\frac{V}{4}

. If the threshold wavelength for the metallic surface is

n\lambda

then value of

n

will be ______.

Official answer

9.00

NTA final key (Sep 2020).

Chapter: Dual Nature of Radiation and Matter
Topic: Photoelectric Effect
Idea tested: Stopping Potential vs Wavelength Graph

Same topic in other shifts

All Photoelectric Effect questions

2 Apr 2026, Shift 1 · Q42For a certain metal, when monochromatic light of wavelength $\lambda$ is incident, the stopping potential for photoelectrons is $3V_o$ .…MediumSingle correct
4 Apr 2026, Shift 1 · Q32The graph shows variation of stopping potential $V_o$ with the frequency $\nu$ of the incident radiation for three photosensitive metals…MediumDiagram basedHas a figure
5 Apr 2026, Shift 1 · Q41Light source having wavelength 331 nm is used to generate photo-electrons whose stopping potential is 0.2 V. The work function of the used…EasySingle correct
8 Apr 2026, Shift 2 · Q38A monochromatic source of light operating at 15 kW emits $2.5 \times 10^{22}$ photons/s. The region of an electromagnetic spectrum to…MediumSingle correct
8 Apr 2026, Shift 2 · Q43 $K_1$ and $K_2$ be the maximum kinetic energies of photoelectrons emitted from a surface of a given material for the light of wavelength…MediumSingle correct
2 Apr 2025, Shift 1 · Q44A monochromatic light is incident on a metallic plate having work function $\phi$ . An electron, emitted normally to the plate from a point…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.