JEE Main 2021 · ChemistryNumerical answerNumerical valueEasyCalculation

JEE Main 4 August 2021, Shift 2, Chemistry Q53

Question 53 of 90 in this shift, Chemistry question 23 of 30, Section B.

The number of photons emitted by a 800 nm lamp having an average power of 5 mW in 10 s is ________

\times\ 10^{17}

. (Nearest integer) [Given : h = 6.626

\times

10^{-34}

Js; C = 3.0

\times

10^{8}

\mathrm{ms^{-1}}

]

Official answer

NTA final key.

Chapter: Structure of Atom
Topic: Photoelectric Effect
Idea tested: Photon Flux and Beam Power

Same idea in other shifts

Asked 7× in all

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4 Aug 2021, Shift 2 · Q29A light source of 25.1 mW emits $2 \times 10^{16}$ photons per second. An unknown metal is brought in front of this light source from…MediumNumerical value
3 Sep 2020, Shift 2 · Q17Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of…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.