Explain what is meant by the term refraction.

The diagram below shows a ray of light travelling from air into the semi-circular glass block.

Draw on this

Describe the position of: (i) the angle of incidence, $i$ (ii) the angle of refraction, $r$

State the equation linking refractive index ($n$), angle of incidence ($i$), and angle of refraction ($r$).

Describe an experimental method to determine the refractive index of the semi-circular glass block using a ray box, a protractor, and a sheet of paper. Your description should include:

• how to set up the apparatus and align the incident ray with the center of the flat face,
• what measurements to take and how to record the paths of the light rays,
• how to obtain a reliable range of results,
• how to use a graph to find the refractive index.