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Radiation is incident on a clean zinc plate causing photoelectrons to be emitted - Scottish Highers Physics - Question 9 - 2017
Question 9
Radiation is incident on a clean zinc plate causing photoelectrons to be emitted. The source of radiation is replaced with one emitting radiation of a higher frequen... show full transcript
Worked Solution & Example Answer:Radiation is incident on a clean zinc plate causing photoelectrons to be emitted - Scottish Highers Physics - Question 9 - 2017
Step 1
Maximum kinetic energy of a photoelectron
Answer
The maximum kinetic energy of a photoelectron is directly related to the frequency of the incident radiation. When we replace the source of radiation with one of a higher frequency, according to the photoelectric effect, the kinetic energy increases. This is described by the equation:
where is the energy of the incoming photon. Since frequency increases, so does the energy of the photon, hence the maximum kinetic energy of the emitted photoelectrons increases.
Step 2
Number of photoelectrons emitted per second
Answer
While the irradiance remains unchanged, the number of photoelectrons emitted per second will decrease because the greater energy of the incoming photons means that each photon may emit fewer electrons, especially if they exceed the work function. Therefore, as the frequency increases and the photon energy increases, fewer photoelectrons will be emitted per second.
Step 3