1. Spot the mistake!

2. BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

3. Learning Objectives
Take a series of measurements to allow you understand how to calculate Magnification.
Practise using the lens equations.
Tuesday, 23 April 2019 4

4. Learning Outcomes
Take a series of results to compare distances and heights in image formation.
Be able to make links between these distances/heights and the magnification of lenses.
Consider and evaluate the uncertainties involved in the experiment.
Grade E
Grade C
Grade A
Tuesday, 23 April 2019 5

5. Investigating magnification...
Using the following pieces of information,
complete 2 ray diagrams and then do the
following:
For each diagram, measure &
record the following:
v (image distance)
hi (image height)
ho (object height)
INFO:
Scenario 1. Scenario 2
f = 4cm f = 5.5cm
u = -2cm u = -2cm
What links can you find between the distances and the heights of the objects and images?
Can you produce an equation linking these things?
NB: THERE WILL BE SOME UNCERTAINTIES HERE
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

6. Lenses and magnification
For a fixed object distance, the greater the power of the lens, the greater the magnification.
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

10. Magnification at GCSE
What does magnification actually mean? If the image is magnified 2 x……
Image height = Object height x 2
MAGNIFICATION = IMAGE HEIGHT
OBJECT HEIGHT
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

11. IF YOU WOULD LIKE TO SEE THE PROOF
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.
Magnification
Magnification is a measure of how much an
image has been enlarged by a lens.
It can be calculated from the heights of the
image and object but also by the distances u and v.
To do this....
M = v u
IF YOU WOULD LIKE TO SEE THE PROOF

12. Investigating Magnification
Starting with u = 1m and gradually reducing it in equal steps so that in turn v changes.
Investigate how v affects the image height.
Record v and image height and then plot a line
graph of your results.
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

13. Sample results image distance / x10-2m image height / x10-2m 18.5 0.35
20.0
0.45
22.0
0.50
23.5
0.60
27.0
0.70
30.0
0.80
37.0
1.10
45.0
1.50
56.0
2.00
Plot a graph of image distance on the x-axis against image height on the y-axis
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

14. Thinking about magnification… copy and complete:
If M is...
The image will be .....
Positive and > 1
Negative and > 1
< 1 =1
= 0
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.

15. Using our graph to find focal length.
What is the significance of our x-intercept? No image height What does that mean in terms of magnification? No magnification
If we know m=0, what does this mean for v and f?
HINT: Think back to lens diagrams from Y11
BY THE END OF THE LESSON: Take a series of results to compare distances and heights in image formation. Be able to make links between these distances/heights and the magnification of lenses. Consider and evaluate the uncertainties involved in the experiment.