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AP EAMCET · PHYSICS · Dual Nature of Matter

A radiation of \(3.8 \mathrm{eV}\) falls on a metal surface to produce photo electrons. These electrons are made to enter a magnetic field of \(2 \times 10^{-4} \mathrm{~T}\). If the radius of the largest circular path followed by these electrons is \(30 \mathrm{~mm}\), then work function of the metal is
(Mass of electron \(\mathrm{m}_{\mathrm{e}}=9 \times 10^{-31} \mathrm{~kg}\) )

  1. A \(0.9 \mathrm{eV}\)
  2. B \(1.0 \mathrm{eV}\)
  3. C \(0.6 \mathrm{eV}\)
  4. D \(1.2 \mathrm{eV}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(0.6 \mathrm{eV}\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & K . E=\frac{q^2 B^2 r^2}{2 \mathrm{~m}} \\ \Rightarrow & K . E=\frac{\left(1.6 \times 10^{-19} \times 2 \times 10^{-4} \times 30 \times 10^{-3}\right)^2}{2 \times 9 \times 10^{-31}} \\ = & 5.06 \times 10^{-19} \mathrm{~J}=3.16 \mathrm{LeV} \\ & \text { So, work…