Download 2013 HSC Physics Marking guidelines

2013 HSC Physics Marking Guidelines
Question 24
Criteria
• Explains how a photocell works, using photoelectric effect
• Includes an appropriate diagram
• Describes how a photocell works, using photoelectric effect
• Outlines how a photocell works, using photoelectric effect
• Outlines how a photocell works, without necessarily mentioning the
photoelectric effect
• Identifies ONE feature of a cell that uses light
OR
• Identifies that a photocell uses the photoelectric effect
Marks
5
4
3
2
1
Sample answer:
A photocell detects light and transforms the energy into electricity using the photoelectric
effect. When light of frequency greater than the threshold frequency of the cathode material
falls on the cathode, photoelectrons are emitted because the electrons have enough energy to
leave the surface of the metal. This is the photoelectric effect. These electrons are collected by
the anode and an electric current starts flowing in the external circuit. The current would stop
if the light does not fall on the cathode or the frequency of the light was less than the
threshold frequency.
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