1.) Why would there be a spread of values in the kinetic energy of liberated pho

Question

1.) Why would there be a spread of values in the kinetic energy of liberated photoelectrons coming off the surface of a photosensitive material illuminated by a monochromatic source?

2.) What might explain the continual decrease in photocurrent that is seen in the data from (6) as the wavelength of the source increases? After all, the intensity of the source remained constant at 100% as you varied the wavelength which would argue that the photocurrent should remain fairly up until you reach there cutoff wavelength ?

K-N DATA FOR SODIUM wavelength bias voltage wave electron K bias voltage 213n -4.00 V -0.00V 0.00 eV n M 100v lonm 1.00 ev -5.00V mm 2.00 ev -6.00V -2.00 V mm nm 15a nm 3.00 eV -7.00V Am -3.00V electron K 4.00 eV 5.00 eV 6.00 eV 7.00 ev

Explanation / Answer

Here we can imagine two reasons for the spread in kinetic energy.

Due to the finite bandwidth of the monochromatic source:

There is no perfect monochromatic source exist so it has some frequency bandwidth. The kinetic energy of the emitted electron is given by subtracting total energy of photon with the ionization potential of the atom. So different frequency photons have different energies and they provide slightly different kinetic energies to the emitted electrons which causes the spread in KE spectrum.

Due to the atomic levels of atom:

When we incident the photon on the surface of the material, then the free electron present in that material gains that energy and come out of the material. there will be slight probability for bound electrons also to get emit which has slightly higher ionization potential that reduces the KE. As this process is random so the KE has finite spectrum i.e. range.

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