1. Light changes direction when moving between different materials due to refraction. Scientists studying refracting telescopes need accurate information on how light refracts when moving between air and glass. 2. An experiment is described where light passes through a semicircular glass block and the angle of refraction is measured for different angles of incidence. 3. The results are plotted on a graph showing the relationship between incident and refracted angles, helping to understand how optics can correct vision problems.

1. 6.4 Bending Light February 17, 2011 What must light be doing to make these images?

4. Equipment: ray box, paper, glass block, protractor 2 Carefully mark the angles on the sheet of paper, making sure that they are lined up with the centre of the flat side of the glass block. 3 Shine the light accurately along the first line so that the light ray hits the centre of the glass block. SAFETY: the ray box will get hot enough to burn you… be careful incident light (light coming in from light source) semi-circular glass block mark refracted light paths in this region paper 80 ° 70 ° 60 ° 50 ° 40 ° 30 ° 20 ° 10 ° 0 °

5. Mark the line of light that comes out of the curved side of the glass block accurately, using a ruler, as shown in the diagram below. 5 Repeat steps 3 and 4 for each of the lines. 6 When you have completed the experiment, remove the glass block and draw a line from the centre of the flat side of the block where the light ray came in to each of the light ray paths that you drew coming out of the curved side. 7 Measure the angle between the straight through line and each light ray. incident light ray semi-circular glass block refracted light ray angle measured here normal

6. Presenting your results Now draw a graph of your results incident angle / o refracted angle / o Refracted angle (  ) 80 70 60 50 40 30 20 10 0 Incident angle (  )