Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. The ratio of threshold wavelength of sodium to that of copper is nearest to
Show Hint
- \(1:4\)
- \(4:1\)
- \(1:2\)
- \(2:1\)
The Correct Option is D
Solution and Explanation
The threshold wavelength is \(\lambda_0 = \dfrac{hc}{\phi}\), so \(\lambda_0 \propto \dfrac{1}{\phi}\).
Step 2: Substitution
\(\dfrac{\lambda_{Na}}{\lambda_{Cu}} = \dfrac{\phi_{Cu}}{\phi_{Na}} = \dfrac{4.5}{2.3}\).
Step 3: Calculation
\(\dfrac{4.5}{2.3} = 1.96 \approx 2\), so the ratio is nearly \(2:1\).
Final Answer:
The ratio is nearest to 2 : 1. \[ \boxed{\text{(D) }2:1} \]
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