જો \(4000\, \mathop A\limits^o \) તરંગલંબાઈનો પ્રકાશ ધાતુમાંથી \(6\times10^5\, ms^{-1}\) વેગ ધરાવતા ફોટોઇલેક્ટ્રોનનું ઉત્સર્જન કરે તો ધાતુનું કાર્યવિધેય ............... \(\mathrm{eV}\) થશે ? ( ઇલેક્ટ્રોનનું દળ \(= 9\times10^{-31}\, kg\) પ્રકાશનો વેગ \(= 3\times10^8\, ms^{-1}\) પ્લાન્ક અચળાંક \(= 6.626\times10^{-34}\, Js\) ઇલેક્ટ્રોનનો વીજભાર \(= 1.6\times10^{-19}\, J\,eV^{-1}\))

A \(0.9\)
B \(3.1\)
C \(2.1\)
D \(4\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(2.1\)

Step-by-step Solution

Detailed explanation

\(hv = \phi + h{v^o}\) \(\frac{1}{2}m{v^2} = hc\left( {\frac{1}{\lambda } - \frac{1}{{{\lambda _0}}}} \right)\) \(hv = \phi + \frac{1}{2}m{v^2}\) \(\phi = \frac{{6.626 \times {{10}^{ - 34}} \times 3 \times {{10}^8}}}{{4000 \times {{10}^{ - 10}}}}\)…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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\(\dfrac{1}{T}(\text{K}^{-1})\)	\(\log_{10} K_p\)
\(0.05\)	\(3.5\)
\(0.06\)	\(2.5\)
\(0.07\)	\(1.5\)