(a) When EM radiation of appropriate frequency or wavelength is incident on a metal surface, it causes electrons to be emitted from the surface. This phenomenon is called photoelectric effect. It is a surface phenomenon. Emission is instantaneous and K.E. of emitted electrons depend on frequency or wavelength of incident photons.~(b) A = Incident light or EM radiations
B = Cathode
C = Photoelectrons
D = Anode
E = Vacuum (Evacuated space)
F = Glass tube

(c)(i) Intensity of the incident radiation
(ii) Energy or frequency of the incident radiation.

(d) Similarities
(i) In both, particles are emitted
(ii) Both are surface phenomenon
(iii) Both involves energy changes
Difference
(i) Evaporation involves molecules while photoemission involves electrons.
(ii) Evaporation causes cooling while photoemission does not.

(e)(i) Thermionic emission.
(ii) Ionization of gases.
(iii) Field emission

(f) Photocells can be used.
(i) To open or close doors automatically
(ii) In automatic switching device.
(iii) In television cameras
(iv) As a burglar alarm
(v) As safety devices in paper mills and related industries
(vi) To produce sounds of varying intensities on film tracks.
~(c)(i) Intensity of the incident radiation
(ii) Energy or frequency of the incident radiation.

(d) Similarities
(i) In both, particles are emitted
(ii) Both are surface phenomenon
(iii) Both involves energy changes
Difference
(i) Evaporation involves molecules while photoemission involves electrons.
(ii) Evaporation causes cooling while photoemission does not.

(e)(i) Thermionic emission.
(ii) Ionization of gases.
(iii) Field emission

(f) Photocells can be used.
(i) To open or close doors automatically
(ii) In automatic switching device.
(iii) In television cameras
(iv) As a burglar alarm
(v) As safety devices in paper mills and related industries
(vi) To produce sounds of varying intensities on film tracks.
~(d) Similarities
(i) In both, particles are emitted
(ii) Both are surface phenomenon
(iii) Both involves energy changes
Difference
(i) Evaporation involves molecules while photoemission involves electrons.
(ii) Evaporation causes cooling while photoemission does not.

(e)(i) Thermionic emission.
(ii) Ionization of gases.
(iii) Field emission

(f) Photocells can be used.
(i) To open or close doors automatically
(ii) In automatic switching device.
(iii) In television cameras
(iv) As a burglar alarm
(v) As safety devices in paper mills and related industries
(vi) To produce sounds of varying intensities on film tracks.
~(e)(i) Thermionic emission.
(ii) Ionization of gases.
(iii) Field emission

(f) Photocells can be used.
(i) To open or close doors automatically
(ii) In automatic switching device.
(iii) In television cameras
(iv) As a burglar alarm
(v) As safety devices in paper mills and related industries
(vi) To produce sounds of varying intensities on film tracks.
~(f) Photocells can be used.
(i) To open or close doors automatically
(ii) In automatic switching device.
(iii) In television cameras
(iv) As a burglar alarm
(v) As safety devices in paper mills and related industries
(vi) To produce sounds of varying intensities on film tracks.
