3.19 describe an experiment to determine the refractive index of glass, using a glass block

Method
- Draw around a rectangular glass block.
- At an angle, shine a ray of light (from a light box) through it. Trace the incident and emergent rays.
- Take away the glass block, draw the refracted ray (by joining up the incident and emergent rays).
- At the point where the ray entered the block, draw the normal at 90º to the edge of where the block was.
- Use a protractor to measure the angle if incidence (i) and the angle of refraction (r). NOTE: remember to measure from the normal line
- Calculate the refractive index (n) using the equation n = sin i / sin r

Presuming all is well, your diagram should look something like this...