The graph which shows the variation of and its kinetic energy, E is (where λ is de Broglie wavelength of a free particle):

Radiation of frequency 2 is incident on a metal with threshold frequency . The correct statement of the following is ____________.
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A point source causing photoelectric emission from a metallic plate is moved away from the plate. The variation of photoelectric current with distance from the source is correctly represented by the graph _____________.
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A proton accelerated through a potential difference V has a de Broglie wavelength λ. On doubling the accelerating potential, de Broglie wavelength of the proton ________________.
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The transfer of integral number of __________ is one of the evidence of quantization of electric charge.
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