First slide

Photoelectric effect and study of photoelectric effect

Question

Work function of lithium and copper are respectively 2.3 eV and 4.0 eV. Which metal will be useful for the photoelectric cell working with visible light? $(h = 6.6 \times 10^{- 34} Js, c = 3 \times 10^{8} m / s)$

Moderate

A

Lithium
B

Copper
C

Both
D

None of these

Solution

From $λ_{0} = \frac{12375}{W_{0}}$
The maximum wavelength of light required for the photoelectron emission, ${(λ_{0})}_{Li} = \frac{12375}{2.3} = 5380 Å$
$Similarly {(λ_{0})}_{Cu} = \frac{12375}{4} = 3094 Å$
The wavelength 3094 $Å$ does not lie in the visible region, but it is in the ultraviolet region. Hence to work with visible light, lithium metal will be used for photoelectric cell.

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