Photoelectric Effects and deBroglie Equation: Practice Problem & Solution
The potential difference that must be applied to stop the fastest photo electrons emitted by a nickel surface, having work function 5.01 eV, when ultraviolet light of 200 nm falls on it, must be: (2010 Pre)
Short Solution (Best for NEET):
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 energy of incident photons is $E = \frac{1240 eV nm}{\lambda(nm)} = \frac{1240}{200} = 6.2 eV$. The maximum kinetic energy of emitted photoelectrons is $K_{max} = E - W = 6.2 - 5.01 = 1.19 eV \approx 1.2 eV$. Therefore, the stopping potential difference magnitude is $1.2 V$ (Often referenced as $1.2 V$ depending on convention for potential difference).
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