Question 238: Dual Nature of Matter and Radiation

Question

A beam of electromagnetic radiation of intensity 6.4 × 10
–5
W/cm
2
is comprised of wavelength,
$$\lambda $$ = 310 nm. It falls normally on a metal (work function $$\phi $$ = 2eV) of surface area of 1 cm
2
. If one
in 10
3
photons ejects an elctron, total number of electrons ejected in 1 s is 10
x
. (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

Integer / Numeric Answer Type