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Saturday, 31 October

JEE Main 2022 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 28 July 2022, Shift 2, Physics Q15

Question 15 of 90 in this shift, Physics question 15 of 30, Section A.

Sun light falls normally on a surface of area 36 cm236\ \mathrm{cm^2} and exerts an average force of 7.2×10−97.2\times10^{-9} N within a time period of 20 minutes. Considering a case of complete absorption, the energy flux of incident light is
  1. (1)25.92×102 W/cm225.92\times10^{2}\ \mathrm{W/cm^2}
  2. (2)8.64×10−6 W/cm28.64\times10^{-6}\ \mathrm{W/cm^2}
  3. (3)6.0 W/cm26.0\ \mathrm{W/cm^2}
  4. (4)0.06 W/cm20.06\ \mathrm{W/cm^2}Official answer

Official answer

Option 4

NTA final key.

Chapter
Electromagnetic Waves
Topic
Thermal Radiation
Idea tested
Thermal Radiation Pressure

Same idea in other shifts

Asked 3× in all
  1. 3 Apr 2025, Shift 1 · Q40The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2m away from it, isMediumSingle correct
  2. 8 Apr 2024, Shift 1 · Q42Average force exerted on a non-reflecting surface at normal incidence is 2.4×10−42.4\times10^{-4} N. If 360 W/cm2^2 is the light energy flux…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 108 of the 174 JEE Main shifts held from 2017 to 2026.