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# Light of intensity 10^-5 W m^-2 falls on a sodium photocell of surface area 2 cm^2. Assuming that the top 5 layers of sodium absorb the incident energy, estimate time required for photoelectric emission in the wave-picture of radiation.

Q: 11.30 Light of intensity   falls on a sodium photo-cell of surface area .  Assuming that the top 5 layers of sodium absorb the incident energy, estimate time required for photoelectric emission in the wave-picture of radiation. The work function for the metal is given to be about . What is the implication of your answer? (Effective atomic area of a sodium atom = 10-20 m2 )

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Intensity of Incident light(I) =

The surface area of the sodium photocell (A)=2 cm2= 210-4 m2

The rate at which energy falls on the photo cell=IA=210-9 W

The rate at which each of the 5 surfaces absorbs energy= IA/5=410-10W

Effective atomic area of a sodium atom (A')= 10-20 m2

The rate at which each sodium atom absorbs energy is R given by

The time required for photoelectric emission is

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