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# Lenses experiment

Extracts from this document...

Introduction

## Hypothesis

I hypothesise that moving the object further away from the focal point of a converging lens will decrease the magnification of the size of the image.

## Apparatus

Method

I will set up the apparatus as shown in the diagram above. To decide which lens I am to use I will find the focal lengths of different lenses and us the lens that gives the easiest focal length to work with, this will be found out in my preliminary experiment.

In this experiment I will be trying to prove my hypothesis, to do that the results that I obtain have to help me find the magnifications of different lengths away from the focal length. The object will be put on the focal point for the first result then I will measure the diameter of the object, this should always be 2.0cm, and then I will measure the diameter of the image. I will record my results into a suitable table; all of my results must be to 1 decimal place apart from the results for the magnifications, which will be to 2 decimal places. I will obtain results every 2.0cm and take four results so that I can take an average result for the object distance (U), for the width of the image and the magnification. I will obtain results every 2.0cm because the image size drastically changes at the beginning when moving it away from the lens just a little bit and less so later on when got past 2F(twice the focal length), therefore a small gap between results is vital or else when coming to make a graph of the results will cause major parts of the magnification change to be lost.

I will choose a suitable range of results from performing the preliminary experiment.

Variables

Middle

Diameter of image/cm

Magnification

10.0

10.0

Indescribable

Immeasurable

/

10.0

10.0

Indescribable

Immeasurable

/

10.0

10.0

Indescribable

Immeasurable

/

10.0

10.0

Indescribable

Immeasurable

/

10.0

12.0

Real, magnified & inverted

9.1

4.55

10.0

12.0

Real magnified & inverted

8.9

4.45

10.0

12.0

Real magnified & inverted

8.8

4.40

10.0

12.0

Real magnified & inverted

8.9

4.45

10.0

14.0

Real magnified & inverted

4.4

2.20

10.0

14.0

Real magnified & inverted

4.6

2.30

10.0

14.0

Real magnified & inverted

4.3

2.15

10.0

14.0

Real magnified & inverted

4.5

2.25

10.0

16.0

Real magnified & inverted

2.9

1.45

10.0

16.0

Real magnified & inverted

3.1

1.55

10.0

16.0

Real magnified & inverted

3.1

1.55

10.0

16.0

Real magnified & inverted

3.1

1.55

10.0

18.0

Real magnified & inverted

2.1

1.05

10.0

18.0

Real magnified & inverted

2.3

1.15

10.0

18.0

Real magnified & inverted

2.1

1.05

10.0

18.0

Real magnified & inverted

2.3

1.15

10.0

20.0

Real same size & inverted

2.0

1.00

10.0

20.0

Real same size & inverted

2.0

1.00

10.0

20.0

Real same size & inverted

2.0

1.00

10.0

20.0

Real same size & inverted

2.0

1.00

10.0

22.0

Real diminished & inverted

1.5

0.75

10.0

22.0

Real diminished & inverted

1.6

0.80

10.0

22.0

Real diminished & inverted

1.6

0.80

10.0

22.0

Real diminished & inverted

1.7

0.80

10.0

24.0

Real diminished & inverted

1.2

0.60

10.0

24.0

Real diminished & inverted

1.3

0.65

10.0

24.0

Conclusion

As you can see my results become increasingly inaccurate as the experiment progressed but was completely accurate when the object distance was 20.0cm, which was in the middle of the experiment.

I could have done this experiment with different sized convex lenses instead of just using the one type, but for this I would have needed a lot more time. I could have done the entire experiment on the same day because the weather on different days can affect the accuracy of the results and dependant on how focused I was on different days could have affected the results but by looking at the results I believe I was on the ball throughout the experiment. Instead of having results in intervals of 2.0cm I could have decreased this to 1.0cm or even 0.5cm. I would not go any lower than this for my accuracy to decimals would not be very accurate. Having a smaller gap between results would allow my to have more results to help me in my graph for at the beginning I do no know what is exactly happening in between the dramatic decline in magnifications.

Two more possibilities when using the same basic equipment would to do more repeats because you can never have enough repeats and to have a larger range in results to possibly see if the magnification is ever equal to 0 or if the magnification eventually goes so far that the magnification stops decreasing.

As far as the use of the apparatus goes I could have changed the odd thing realistically. I could have changed the light source from a lamp which is not a light source that gives off parallel rays of light I could have used a light source that gave off parallel rays of light for example the sun, but that would not be a very good thing to use in England because the amount of sunlight given off always changes according to typical English weather.

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