Learn

Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 3 September 2020, Shift 2, Physics Q17

Question 17 of 75 in this shift, Physics question 17 of 25.

Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of the same power 200 W. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is :
  1. (1)1250\frac{1}{250}
  2. (2)250
  3. (3)1500\frac{1}{500}Official answer
  4. (4)500

Official answer

Option 3

NTA final key (Sep 2020).

Chapter
Dual Nature of Radiation and Matter
Topic
Photoelectric Effect
Idea tested
Photon Flux and Beam Power

Same idea in other shifts

Asked 7× in all
  1. 1 Feb 2024, Shift 2 · Q46Monochromatic light of frequency 6×10146\times10^{14} Hz is produced by a laser. The power emitted is 2×10−32\times10^{-3} W. How many photons per…EasySingle correct
  2. 26 Jul 2022, Shift 1 · Q34A parallel beam of light of wavelength 900 nm and intensity 100 Wm−2100\ \mathrm{Wm^{-2}} is incident on a surface perpendicular to the beam.…MediumSingle correct
  3. 30 Jun 2022, Shift 1 · Q48A source of monochromatic light liberates 9×10209\times10^{20} photon per second with wavelength 600 nm when operated at 400 W. The number of…EasySingle correct
  4. 3 Aug 2021, Shift 1 · Q18An amount of 8×10208 \times 10^{20} photons per second are emitting from a monochromatic source of light operated at 500W, with 80%…MediumSingle correct
  5. 4 Aug 2021, Shift 2 · Q29A light source of 25.1 mW emits 2×10162 \times 10^{16} photons per second. An unknown metal is brought in front of this light source from…MediumNumerical value
  6. 4 Aug 2021, Shift 2 · Q53The number of photons emitted by a 800 nm lamp having an average power of 5 mW in 10 s is ________ × 1017\times\ 10^{17}. (Nearest integer)…EasyNumerical value

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 108 of the 174 JEE Main shifts held from 2017 to 2026.