Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. If the frequency is halved and intensity is doubled, the photoelectric current becomes
Correct answer: D. zero
- A. four times
- B. half
- C. double
- D. zero
Explanation
In the photoelectric effect, the emission of electrons depends on the energy of the incident photons, not just their intensity. Even if the intensity is doubled, if the frequency is halved and it remains below the threshold frequency, no photoelectric current will be produced. The photoelectric effect requires photons with energy greater than or equal to the work function of the material to eject electrons.Incorrect Options and Explanations: (a) four times - The photoelectric current cannot increase if the frequency of the incident light is halved below the threshold frequency. (b) half - Halving the frequency below the threshold frequency would prevent the emission of photoelectrons, resulting in zero current. (c) double - Doubling the intensity alone might increase the number of ejected electrons, but halving the frequency below the threshold frequency negates the photoelectric effect.
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Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.
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