Method for investigating light refraction on different substances

Place transparent rectangular block on a piece of paper and trace around it Use ray box to shine a ray of light at the middle of one side of a block Trace incident ray and mark where it emerges on other side of block Remove block and join incident ray with reflected ray Draw the normal at the point where the IR entered the block Measure the angle between the IR and normal, and the angle between the refracted ray and the normal Repeat using different blocks of material keeping the incident angle the same