Key Stage 5
Increasing intensity of light
Quantum quirks
Pupil worksheet
What is light?
This is a question that scientists
have struggled with for centuries.
Light has no mass but it is obvious
that it exists. It can travel from
place to place at incredible speeds
but how does it move? If you
were to magnify a ray of light
what would you see?
Following many years of investigation, we have got to the point where we
have a good understanding of the nature of light. This knowledge has unlocked
the potential for light to be used for many exciting new applications. Scientists
at the University of Oxford are amongst those developing new ways of using
light which could be used to produce driverless cars, super-computers and
powerful telescopes.
Light investigations
Isaac Newton studied how light obeyed strict rules such as the law of
reflection. Light bounces off a mirror at the same angle that it hit it - much like
a pool ball hitting a cushion. He concluded that therefore, light must consist of
particles - like lots of tiny balls.
In 1801 Thomas Young carried out his now famous 'double slit experiment'. His
observations of interference patterns showed that light was behaving like a
wave.
http://www.oxfordsparks.ox.ac.uk/run-for-your-light
So how does light behave - as a stream of particles or as a wave?...
...or could it be both?
Your task
We now know that light, like all EM radiation, behaves like packets of energy
called quanta or photons.
A version of Young's experiment can be set up where single photons are sent
through the double slits.
1.
2.
On the next pages, fill in the boxes to write your prediction, method,
results and conclusion.
Complete your conclusion by using the information on the final page to
write a scientific explanation for your results.
Key Stage 5
Key Stage 5
Quantum quirks
Quantum quirks
Equipment
Equipment
Prediction
Photons are fired at the double slit one at a time. Use the blank bar
chart axis to show what pattern you would expect to see on the
detector after one second.
Prediction
Photons are fired at the double slit one at a time. Use the blank bar
chart axis to show what pattern you would expect to see on the
detector after one second.
100
Photons counted
Photons counted
100
80
60
40
20
60
40
20
3.8
4
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
0
3.8
4
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
0
80
Position (mm)
Position (mm)
http://www.oxfordsparks.ox.ac.uk/run-for-your-light
Key Stage 5
Key Stage 5
Quantum quirks
Quantum quirks
Results 1
Results 1
The data after one second is shown below.
The data after one second is shown below.
100
80
Photons counted
60
40
20
80
60
40
20
0
3.8
4
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
0
Position (mm)
Is this consistent with your prediction?
Suggest an explanation for the results.
http://www.oxfordsparks.ox.ac.uk/run-for-your-light
3.8
4
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
Photons counted
100
Position (mm)
Is this consistent with your prediction?
Suggest an explanation for the results.
Key Stage 5
Key Stage 5
Quantum quirks
Quantum quirks
Results 2
The data after 5 minutes is shown below. A pattern has arisen.
The data after 5 minutes is shown below. A pattern has arisen.
320
320
280
280
Photons counted
Photons counted
Results 2
240
200
160
120
80
40
240
200
160
120
80
40
0
0
3.8 4.1 4.4 4.7 5 5.3 5.6 5.9 6.2 6.5 6.8 7.1 7.4 7.7 8 8.3 8.6
Position (mm)
The conclusion from this experiment is that photons sometimes display
wave-like properties. Explain how the data shows this.
Hint: Look at the interference pattern on page 1.
http://www.oxfordsparks.ox.ac.uk/run-for-your-light
3.8 4.1 4.4 4.7 5 5.3 5.6 5.9 6.2 6.5 6.8 7.1 7.4 7.7 8 8.3 8.6
Position (mm)
The conclusion from this experiment is that photons sometimes display
wave-like properties. Explain how the data shows this.
Hint: Look at the interference pattern on page 1.