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  • A beam of electromagnetic radiation of intensity  is comprised of wavelength <img alt="\lambda=310 nm" src="htt

A beam of electromagnetic radiation of intensity 6.4\times10^{-5} W/cm^2 is comprised of wavelength \lambda=310 nm. It falls normally on a metal (work function \phi=2 eV) of surface area 1 cm2. If one in 103 photons ejects an electron, total number of electrons ejected in 1s is 10x (hc=1240 eVnm, 1 eV=1.6 x 10-19J), then x is :-  
Option: 1 11
Option: 2 10
Option: 3 12
Option: 4 13

Answers (1)

best_answer

Energy in 1 second = 6.4 \times 10 ^{-5} \times \1 \ \times 1 = 6.4 \times 10 ^{-5} Joule

Energy (eV) = \frac{6.4 \times 10 ^{-5}}{1.6 \times 10^{-19}} = 4 \times 10^{14} eV

Energy \ of\ one\ photon = \frac{12400}{3100} = 4 \ eV

Number \ of \ photon \ = \frac{4 \times 10^{14}}{4} = 10^{14}

Number \ of \ electrons \ = \frac{10^{14}}{10^3} = 10^{11}

So, \ x = 11

So the correct answer is option 1.

Posted by

Ritika Jonwal

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