2- To determine the refractive index of a transparent solid medium e.g. perspex or glass.
Theory.
The refractive index (n) of a transparent material can be determined by measuring the angle of incidence and the angle of refraction as a ray of light enters, or leaves the material. Refractive index is a number that indicates how fast light travels in a transparent medium. The higher the refractive index the slower the speed of light in that medium.
Variables.
Independent - angle of incidence (i)
Dependent - angle of refraction (r)
Controlled - list everything else here...
Diagram. What to measure and how?  Manipulate - angle of incidence (i) Record - angle of refraction (r) Method 1 Place the perspex block on the white paper and trace the outline. 2 Shine a single incident ray onto the block, mark its path and draw the incident ray with a ruler. 3 Mark the path of the ray emerging from the block, draw ray with a ruler. 4 Remove the block, connect the entry and exit points to show the path of light inside the block. 5 Draw a normal at the entry point, measure the angle of incidence (i) and angle of refraction (r ) using a protractor. 6 Repeat for a range of angles of incidence. RESULT |
Plot a suitable graph with sin r on the x-axis and sin i on the y-axis.
Gradient = rise / run = sin i / sin r = n
Calculate the gradient of the graph to get the refractive index of the transparent material.
Conclusion.
As the angle of incidence (i) is increased the angle of refraction (r)...
The refractive index of perspex/glass was...
