# An Investigation to see how the size of ashadow depends on the angle at which the light hits the object

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Introduction

An Investigation to see how the size of a shadow depends on the angle at which the light hits the object

## Introduction

The aim of the project is to see which factors affect the size of a shadow and then to look more closely at one of the factors to see how exactly it varies the size of a shadow.

## Variables that may affect the size of the shadow

Although, I will investigate how one factor affects the size of a shadow, there are other factors that could be investigated. Here are some examples:

- The distance between the light and the object

From the ray diagrams I can see that as the distance from the object to the light source is doubled, the length of the shadow decreases. A distance of 4cm produces a shadow of approximately 1.6-cm. Decreasing the distance to 2cm(half the distance), the shadow size increases by one and a half times to produce a shadow of 2.3 cm. The three ray diagrams together show the increase of the distance between the object and light source, decreasing the length of the shadow.

2) The distance between the object and the screen

The results from this are opposite varying the previous factor.

Middle

5) The angle at which the screen is

This shows that by increasing the angle the screen is held at, increases the length of the shadow. As I have not measured the angles I cannot compare the increase of angle to the length of shadow in numerical form, but this could be further investigated.

6) The size of the object

This is an obvious effect but it still is a factor as it affects the size of the shadow in a directly proportional way i.e.: the bigger the object, the larger the size of shadow.

7) The angle at which light hits the object

This shows by increasing or decreasing the angle the length of the shadow increases. By increasing the angle to 20º the length of shadow changes from 1.9cm to 2.6 i.e.: it increases by 1.3 times.

I have decided to investigate how varying the angle at which light hits the object affects the size of a shadow. It is important that all the other factors are kept constant in all my experiments; otherwise I would not be finding the effect of the factors, but of a mixture of factors. Therefore these factors will be kept constant.

- The distance between the light and the object: I will keep this constant by moving the light in a semi-circle, where the distance between the light and the object will stay the same.
- The distance between the object and screen: The screen and the object will not be moved throughout all the experiments.
- The light source
- The shape of the object: The same object will be used each time.
- The angle at which the screen is: The screen will be clamped 90º to the ground and will not he altered.
- The size of the object: The same object will be used each time.

Conclusion

From this I realised that

- A 12V torch bulb would suit me better as the bright light created a darker shadow than the 5V bulb, which was very dim. A darker shadow was more vivid than the fainter shadow, therefore easier to take measurements from.
- Moving the object and changing it with other objects made me realise that a 2D shade didn’t stay upright very well. I decided not to opt for the scissors because as it was difficult to measure the size of the shadow.In the end I chose a 3D rectangular block.
- Standing the block upright was a better than leaving it lying on its wider base as it was hard to see the edges of the shadow, when it was lying flat.

## Strategy

Apparatus list:

- A large screen
- A 12V torch bulb and a power supply
- A rectangular block
- A sheet with a large protractor drawn on it indicating the angles I will place the light at

I need to change the angle by 15º each time i.e.: 15º further away from the starting line each time. I will measure the length and width of the shadow in order to work out the areas. The ruler will be marked with cm’s and mm’s. I will measure to the nearest .

This student written piece of work is one of many that can be found in our GCSE Comparing length of words in newspapers section.

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