Refraction can be seen in many public areas around ourselves. Like for example a swimming pool looks less deep than it really is and a stick appears to bend when you one end under the water. These effects are caused due to the bending of light rays when light passes from one medium/material into another. Materials such as glass and water are said to be optically more dense compared to air.
In refraction the light ray entering the Perspex (incident ray) hits the Perspex block at a specific angle and enters another medium. Before hitting the Perspex block the light ray was traveling through the air and as soon as it touches the block it enters the glass, which is said to be another medium. Glass is said to be a shallower material and therefore when the light enters the medium its direction changes and the speed is reduced. But because the light ray is hitting at an angle, which is against the normal angle, one side of the light gets into the contact of the Perspex block before the other side. Therefore the speed reduces, thus reducing the wavelength and the impact on the other side of the medium. Hence the light changes its direction and thus it refracts.
When the light ray leaves the Perspex block it enters another medium, which has a deeper surface. Thus its speed increases and wavelength to also increase and it travels faster. This causes the light hitting the air medium at a specific angle against the normal. As a result the light bends away from the normal and thus has refracted. So in refraction when the light ray will hit the Perspex block at an angle coming from the air the light ray will refracts towards the normal. And while the light ray leaves the Perspex block into the air it will bend away from the normal.
If we look at the results retrieved the relationship between the sin (i) and sin (r) is said to be as refractive index of the Perspex block. Refractive index simply gives the indication of how much the light will bend after entering a specific medium or the Perspex block. As I have found from our results the refractive index of the Perspex block is 1.5. Therefore this tells us that when the light hits the Perspex block at any angle the refracted ray will always be less than the incident ray.
In conclusion I have found out that the refractive index of the Perspex block is 1.5. As the angle of incidence increases, the angle of refraction also increases with the sine ratio of 1.5.
Evaluation:
During a practical it is possible that I might have made a error without knowing. Below I have listed some of the errors I could have made which could have given me incorrect results.
- The incident ray and the refracted ray drawn could have been incorrect. Therefore this would be giving incorrect angle results.
- The angles measured from the sheet could be incorrect and thus the refraction index could be wrong.
- The block might not have been drawn correct and thus causing incorrect results.
Even though human error can’t be avoided, as no humans are 100 % perfect, it is possible to improve on those errors. It is possible to avoid them until a maximum amount. Below I have listed how the results could be improved:
- (for error 1) Use a sharp pencil in order to draw the lines of the rays. Draw the rays carefully taking your time and later on using a ruler.
- (for error 2) In order to have the angles correct, use a accurate protractor and remember to have the protractor exactly on the line. To have it more accurate, have several people check it, in which case the results would be accurate.
- (for error 3) See that the block is exactly parallel to the edges of the paper. Using a rule measure from the side of the paper and see that the edges are exactly the same at both sides of the block.
The improvements written above could give more accurate results and might avoid human error. This experiment can be extended further in order to achieve further results. Below is listed the ways of extending this experiment:
- Using a different shape, like a semi circular shape.
- By improving on the improvements and trying to achieve more accurate results.
- Having more tries/attempts from different angles in order to achieve the most accurate refractive index.
- Using a different material other than glass as the materials have different densities.
- Instead of keeping the light on one level with the glass, have the light coming from a different height and check what happens to the light further.