Before starting, drawing around the prism
ensures that the prism can be readjusted if knocked or moved. An additional
insurance can be made by performing this experiment in a dark room, as then the
light is more visible and therefore less mistakes are to be made when following
the lights pathway.

                  A
white light directed through the one of the two shorter edges of the triangular
block. The light then came out of the block’s hypotenuse. The pathway should be
marked just before the light entered and just after the light exited the block.

After this is done, the block can then be removed and in the white space where
the block once laid, the entry and exit points can be joined. The point where
the block leaves the hypotenuse, a perpendicular line should be draw. Then, two
opposite angles should be taken between the normal and the pathway of light (as
demonstrated in diagram 3)

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                                    The two angles can then see
substituted into Snell’s law (see equation 1). Rearranging the equation allows
the unknown medium’s refractive index to be solved, as we know the refractive
index of air is 1.00. This methodology can be repeated several times to gain a
greater amount of precision, and can then be repeated for the other medium.

 

 

 

Diagram 3: how
to label the angles in respect to the normal

 

 

 

 

 

Part B: parallax method:

 

A bench with two pins on either side of a
convex lens should be set up. Using this set up, the focal length of the lens
can be solved. Changing the object pin, the independent variable, should be
changed several times to different lengths of ‘u’ – distance between the pin
and the lens. By changing this, we can then change the dependent variable, the
‘image-finder’ pin. As shown in diagram 2, the ‘image finder’ should be
adjusted so at eye-level the two pins just meet. Due to error associated with
this point being visually decided, a second opinion should be taken to whether
they are just touching. The distance between the ‘image-finder’ pin and the
lens can be labelled as ‘v’. This can then be repeated, so there are several
pairs of u and v values. As discussed in the theory, using equation 4, a graph
can be plotted to find the focal length. Comparing this to the general equation
of a straight line, , the gradient of the line of best fit can be allocated to the
focal length. 

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