Photoelectric Effects and deBroglie Equation: Practice Problem & Solution
38. A photo-cell is illuminated by a source of light, which is placed at a distance d from the cell. If the distance become d/2, then number of electrons emitted per second will be: (2001)
Solution Explained:
To solve this problem, we apply the core principles of Photoelectric Effects and deBroglie Equation. Understanding the underlying formula is key to arriving at the correct answer below:
The intensity of incident light $I$ varies with distance as $I \propto \frac{1}{d^2}$ . When the distance is halved to $d/2$ , the intensity becomes $\frac{1}{(1/2)^2} = 4$ times its original value. Since the number of photoelectrons emitted per second is directly proportional to intensity, it also becomes four times.
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