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A point source of light emits photons of energy $4.8 \mathrm{eV}$ at the rate $10^5$ photons per second. These photons incident on a photo-sensitive sphere of work function $2.8 \mathrm{eV}$ and radius $9 \mathrm{~mm}$. The sphere is initially neutral and the emitted photo electrons are instantly swept away. The time after which the photo electric emission stops is
PhysicsDual Nature of MatterAP EAMCETAP EAMCET 2017 (24 Apr Shift 2)
Options:
  • A $250 \mathrm{~s}$
  • B $125 \mathrm{~s}$
  • C $375 \mathrm{~s}$
  • D $175 \mathrm{~s}$
Solution:
1090 Upvotes Verified Answer
The correct answer is: $125 \mathrm{~s}$
No solution. Refer to answer key.

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