Light 
Q1.
The diagram shows the apparatus that a student used to investigate the heating effect of different wavelengths of light.
 
(a)     (i)      The student put thermometer D outside of the light spectrum.
Suggest why.
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(1)
(ii)    The table gives the position and reading of each thermometer 10 minutes after the investigation started.
 
Thermometer	Position of thermometer	Temperature in °C	
A	in violet light	21	
B	in green light	22	
C	in red light	24	
D	outside the spectrum	20	
What should the student conclude from the data in the table?
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(2)
(b)     A similar investigation completed in 1800 by the scientist Sir William Herschel led to the discovery of infrared radiation.
Suggest how the student could show that the spectrum produced by the glass prism has an infrared region.
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(2)
(c)     A person emits infrared radiation at a frequency of 3.2 x 1013 Hz.
Calculate the wavelength of the infrared radiation that a person emits.
Take the speed of infrared radiation to be 3.0 x 108 m/s.
Show clearly how you work out your answer.
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Wavelength = _________________________ m
(2)
(d)     A thermal imaging camera detects infrared radiation. Electronic circuits inside the camera produce a visible image of the object emitting the infrared radiation.
At night, police officers use thermal imaging cameras to track criminals running away from crime scenes.
Thermal imaging cameras work better at night than during the day.
Explain why.
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(2)
(Total 9 marks)