What are the salient features of the phenomenon of Photoelectricity?
Detailed quantitative investigations on the phenomenon of Photoelectricity show that this phenomenon has the following salient features:
(i) When light (of suitable frequency) shines on a (sensitive) metal surface, the latter emits electrons.
(ii) The phenomenon of photoemission is an instantaneous phenomenon. We start getting emission of photoelectrons as soon as’ light falls on the metal surface.
(iii) The photoelectric current obtained with a given light (light of a particular frequency) is directly proportional to the intensity of the incident light.
(iv) All the emitted photoelectrons do not have the same energy. There is an energy distribution from zero to certain maximum value, say Emax, amongst the emitted photoelectrons.
(v) The maximum energy of the emitted photoelectrons - for light of a given frequency is independent of the intensity of the incident light.
(vi) The maximum energy of the emitted photoelectrons is found to be directly proportional to the frequency of the incident light (vii) For each emitting surfaces, there is a (critical) minimum frequency of the incident light below which photoemission from that surface does not take place. We call this minimum frequency as the threshold frequency of the given surface.
(viii) We get instantaneous photoemission for incident light frequencies greater than the threshold frequency. This happens even at very low intensities. However, if the incident light frequency is less than the threshold frequency, photoemission does not take place.
(ix) For a given frequency of the incident light, the photoelectric current becomes zero at a particular (minimum) value of the negative potential of the anode with respect to the cathode. We call this potential as the stopping potential for that frequency.
(x) The values of the stopping, potential (V) for a given surface, are directly proportional to the frequencies of the incident light.
(xi) The stopping potential V/s frequency graphs for different metals all have the same slope but different intercepts on the frequency axis as shown in Fig. alongside, It means that the graphs for different metals are alt straight lines parallel to each other.
Detailed quantitative investigations on the phenomenon of Photoelectricity show that this phenomenon has the following salient features:
(i) When light (of suitable frequency) shines on a (sensitive) metal surface, the latter emits electrons.
(ii) The phenomenon of photoemission is an instantaneous phenomenon. We start getting emission of photoelectrons as soon as’ light falls on the metal surface.
(iii) The photoelectric current obtained with a given light (light of a particular frequency) is directly proportional to the intensity of the incident light.
(iv) All the emitted photoelectrons do not have the same energy. There is an energy distribution from zero to certain maximum value, say Emax, amongst the emitted photoelectrons.
(v) The maximum energy of the emitted photoelectrons - for light of a given frequency is independent of the intensity of the incident light.
(vi) The maximum energy of the emitted photoelectrons is found to be directly proportional to the frequency of the incident light (vii) For each emitting surfaces, there is a (critical) minimum frequency of the incident light below which photoemission from that surface does not take place. We call this minimum frequency as the threshold frequency of the given surface.
(viii) We get instantaneous photoemission for incident light frequencies greater than the threshold frequency. This happens even at very low intensities. However, if the incident light frequency is less than the threshold frequency, photoemission does not take place.
(ix) For a given frequency of the incident light, the photoelectric current becomes zero at a particular (minimum) value of the negative potential of the anode with respect to the cathode. We call this potential as the stopping potential for that frequency.
(x) The values of the stopping, potential (V) for a given surface, are directly proportional to the frequencies of the incident light.
(xi) The stopping potential V/s frequency graphs for different metals all have the same slope but different intercepts on the frequency axis as shown in Fig. alongside, It means that the graphs for different metals are alt straight lines parallel to each other.
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