Question 258: Dual Nature of Matter and Radiation

Question

A beam of electromagnetic radiation of intensity 6.4 × 10–5 W/cm2 is comprised of wavelength,
$$\lambda $$ = 310 nm. It falls normally on a metal (work function $$\phi $$ = 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 _____.

Accepted Answer

Energy of photon = $${{1240} \over {310}}$$ = 4 eV
Energy is greater than work function so photoelectric effect will take place.
Number of photons =
Intensity
Energy of one photon
= $${{6.4 	imes {{10}^{ - 5}}} \over {4 	imes 1.6 	imes {{10}^{ - 19}}}}$$ = 10
14
Total number of electrons = $${{{{10}^{14}}} \over {{{10}^3}}}$$ = 10
11

Dual Nature of Matter and Radiation

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