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QJEEM20Pha8bd: JEE Main 2020 Physics - Class 12 JEEM20Pha8bd Solution: A beam of electromagnetic radiation of intensity 6.4 × 10 –5…

A beam of electromagnetic radiation of intensity 6.4 × 10–5 W/cm2 is comprised of wavelength, λ\lambda = 310 nm. It falls normally on a metal (work function ϕ\phi = 2eV) of surface area of 1 cm2. If one in 103 photons ejects an elctron, total number of electrons ejected in 1 s is 10x. (hc = 1240 eVnm, 1eV = 1.6 × 10–19 J), then x is _____.

Step-by-Step Verified Solution

Energy of photon = 1240310{{1240} \over {310}} = 4 eV

Energy is greater than work function so photoelectric effect will take place.

Number of photons =
Intensity
Energy of one photon

= 6.4×10−54×1.6×10−19{{6.4 \times {{10}^{ - 5}}} \over {4 \times 1.6 \times {{10}^{ - 19}}}} = 1014

Total number of electrons = 1014103{{{{10}^{14}}} \over {{{10}^3}}} = 1011

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