First slide

Photoelectric effect and study of photoelectric effect

Question

Light of wavelength 180 nm ejects photoelectrons from a plate of metal whose work-function is 2 eV. If a uniform magnetic field of 5 $\times$ 10^-5 T be applied parallel to the plate, what would be the radius (in m) of the path followed by electrons ejected normally from the plate with maximum energy?

Moderate

Solution

$\begin{array}{l} E = \frac{12375}{1800} = 6 .875 eV \\ \begin{aligned} K_{max} or K & = E - W = 4 .875 eV \\ r & = \frac{\sqrt{2 Km}}{Bq} \\ = \frac{\sqrt{2 \times 4 .875 \times 1 .6 \times 10^{- 19} \times 9 .1 \times 10^{- 31}}}{5 \times 10^{- 5} \times 1 .6 \times 10^{- 19}} = 0 .148 m \approx 0.15 m \end{aligned} \end{array}$

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