JEE MainPhysicsDual Nature of RadiationMCQ+4 / −1
For the photoelectric effect, the maximum kinetic energy of the photoelectrons is plotted against the frequency of the incident photons as shown in figure. The slope of the graph gives 

- APlanck's constant
- BWork function of the metal
- CCharge of electron
- DRatio of Planck's constant to electric charge
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Correct answer: A
- For photoelectric effect, Einstein’s photoelectric equation is where:
- = maximum kinetic energy of emitted photoelectrons
- = Planck’s constant
- = frequency of incident radiation
- = work function of the metal
- Compare this with the equation of a straight line: Here,
- slope
- intercept
-
Therefore, when maximum kinetic energy is plotted against frequency, the slope of the graph is which is Planck’s constant.
-
Check options:
- A: Planck's constant ✅ Correct
- B: Work function of the metal ❌ This is related to the intercept, not slope
- C: Charge of electron ❌ Not the slope here
- D: Ratio of Planck's constant to electric charge ❌ This would appear if stopping potential were plotted against frequency
Hence, the correct answer is A.
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