Investigating the factors which affect the sideways displacement of a light ray through a glass block.

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                                   Physics Coursework:

Investigating the factors which affect the sideways displacement of a light ray _                                 through a glass block

Plan:

Refraction: Refraction occurs when light travels from one medium to another in which the speed of light is different. The speed in glass is slower than its speed in air so light is refracted when it travels for air to glass, or vice versa. This change in speed usually results in a change in the direction in which light travels.

Aim: I'm going to investigate the factors, which affect the path of a light ray through a glass block.

These factors are:        

  • Angle of incidence
  • Material
  • Thickness of material

The factor I have chosen is the angle of incidence because it is the easiest to carry out in the classroom since it would be difficult to find different materials that could be tested. Also it would be difficult to find one material with different thickness (to overcome that more than one of the materials could be put together however it would not be completely accurate since there will be a small gap between the two or more pieces.

The experiment I am going to carry out is an experiment to show the sideways displacement of a light ray through a Glass Block.

Apparatus:                                                 

1)Glass block (60 mm wide)

                                                        

2)Ray Box  (with as narrow ray as possible for more precision in measuring the angles)

        

3)Protractor  (with a small scale for more accuracy)

4)Ruler  ( a mm ruler to be more precise measuring)

5)Pencil  (with a sharp point for grater accurately when plotting points and drawing lines)

6)Piece of white paper

Diagram1:

        

                                        

Experiment method: As shown in the diagram: I am going to place the glass block on a white piece of paper. I am going to draw around the glass block with the sharp pencil. On the paper I am also going to draw a normal (line 90 degrees to the glass block). By the help of the large-scaled compass, I am going to measure and then draw on the piece of paper 8 lines going from 10 to 80 degrees from the normal creating 8 different angles of incidence. Then I will send a ray from the ray box along the direction of the incident ray when the angle of incidence is 10 degrees. I will then mark the emerging ray with two dots and later remove the glass block and join the dots together and label them. Then I will extend the incident ray so that it continues through and out of the glass block. This is called the original ray. To find the sideways displacement I must measure using a mm ruler the length between the emerging ray and the original ray.

        This I will do for 0, 10,20,40,50,60,70 and 80 degrees. I will not do more that 80 degrees because from previous experiments I have found that it is very difficult to obtain results with an angle of incidence higher than 80 degrees. I must repeat each twice and make an average for more accuracy. If I see that the two results are unacceptably different I must record a third result and eliminate the incorrect result (the one visibly different to the other two).  

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How to collect results:

Results table:

Graph:

Fair Test: We must make sure that the same equipment is used. For example if we take more than one lesson to do the experiment, the same glass block must be used because different glass blocks may have different sizes and other features. Also I must repeat the experiment. At the beginning I'm going to do a practice experiment for which the obtained results I will not count. Then I will do the experiment twice, recording the data and ...

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