Investigating light and refraction using a glass block.

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Peter Sené                Physics coursework

Investigating light and refraction using a glass block


Light is a type of wave. It moves in peaks and troughs (in other words, oscillates). The wavelength of visible light is only 1/2000 of a millimetre! It moves as shown below:


                1/2000 cm

Light travels very quickly (roughly 300million metres per second!) through air, as it is not very dense. When it enters something denser, like water or glass, it slows down. If it enters this denser substance at 90 º then it passes straight though without being bent/refracted. This is line is shown on diagrams as the “normal”. This is used to measure angle of refraction and reflection because it stays straight even if the mirror is bent. If a ray of light enters the denser object at an angle then the ray is refracted (bent) and exits the substance in a different place (see diagram below).

The rays of light are refracted because as the waves of light are quite long (in width). This means that as one part of the wave of light may be entering the glass block and therefore slowing down, another part will going at the same fast speed of 300 million metres a per second. This makes the ray of light turn like a tank, therefore refracting it.

Statement of intent

I plan to change the angle of incidence as the rays of light enter a glass blocks and record the angle of incidence and refraction to see how they effect each other.

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I predict that whatever the angle of incidence is, it will be larger then the angle of refraction because the light will be entering something denser, so the wave nearest the “normal” will enter the block first, causing the ray to turn towards the normal, reducing the angle size.

Keeping the experiment fair

In this experiment I will be only changing one variable, which will be the size of the angle of incidence. This means I will have to have to keep all the other variable the same. To do this I will use the same ray ...

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