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Carry out an experiment to find a relationship between the incident angle and the refracted angle when light is shone through a rectangular Perspex block.

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Introduction What is refraction? Refraction is the bending of the path of a light or sound wave as it passes across the boundary separating two mediums. If a wave of light travels from one medium to another the direction is changed. Refraction is caused by the change in speed experienced by a wave when it changes medium. A wave doesn't just stop when it reaches the end of a medium there will be some reflection off the boundary and some transmission into the new medium. The wave undergoes refraction as it approaches the medium. This can be demonstrated by shining a beam of light through a block of rectangular glass. Refraction also causes the wave length to change but the frequency never changes. How does refraction happen? Light slows down as it hits a denser medium for example, glass. If you were to direct a beam of light at a glass block you will see that the light changes direction when entering the glass. The reason for this is when the light comes into contact with the glass at an angle; one edge of the light beam slows down before the other. This causes the light to bend towards the normal until both edges are travelling at the same speed. ...read more.


Angle of incidence Refracted angle Mean of results 0� 0� 0� 30� 20� 25� 40� 23� 31.5� 45� 25� 35� 60� 32� 46� According to the table above, the refracted angles are about half of the angles of incidence. 60� and 32�, 40� and 23� are examples of this. 0� doesn't change, because the different sides of the light beam slow down at the same time, which stops the light from bending. The refracted angle furthest away from the incident angle is 20�. This is 5� from what I would have expected. I repeated this angle once more and obtained the following result. . 30� 17� 23.5� This final result seems to be more accurate when compared with the original result of 20�. The first result may have had some inaccuracies, as the light may not have been shone directly from 30�. In this experiment, you can measure the amount of refraction that takes place in any boundary by measuring the refracted angle. To find the any given boundary we can compare the angle of refraction to the angle of incidence. The lights speed can make a large difference to the angle of refraction. Analysis of results Below is a graph to show the table of results. ...read more.


Equipment used For this experiment I will need: * A light box. * A light slit. * A semi-circular Perspex block. * A power pack. * A protractor. * A ruler. * A pen or pencil. * A sheet of paper. Method I will draw around the Perspex block; this will then enable me to draw in the normal and the selected angles. I will shine the beam at the Perspex from the selected angles. Marking crosses at the point the light exits the Perspex and where the light continues. Then, when I connect these lines I will be able to measure the angle of refraction with the protractor. Table of Results Angle of incidence Refracted angle 0� 0� 10� 17� 20� 30� 30� 50� 40� 74� 50� 134� 60� 124� Below is a graph showing my results for this experiment. This graph is showing that as the angle of incidence increases, the refracted angle also increases. It follows a curved shape. The result found for 50� seems to be the only incorrect result; this could be because of the beam of light not being placed directly on the selected angle. The rest of the results seem accurate as they follow a predictable pattern. As in the wave theory, the curve of the graph follows a slight transverse wave pattern. Joe Ramage 11H Candidate number: Teachers name: Investigating the refraction of light Joe Ramage 11H ...read more.

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