Learning Aims: 

Materials: 
Red laser pointer, Block of glass, White paper, Pencil, Protractor

Suggestions for use: 
The students should be given the materials and asked to discuss how they might go about studying what happens to the direction of light when a laser passes from air into glass and back into air. The students should examine questions such as:
Next, the students perform the experiment they have devised and report their results in Worksheet 2.2. If they have standardised their measurements, the data can be entered into a software package such as Excel and projected on a screen for the students to see. A plot of ‘angle of incidence’ versus ‘angle of refraction’ will not yield a straightline graph and the teacher should then show the students how this changes if the Sine (or Cosine, depending on whether the students have measured the angle from the normal or surface of the glass) of the angles are plotted. The students can then use the slope of this line to extract the ‘refractive index of glass’ (assuming the refractive index of air is 1) and hence extract Snell’s Law. Finally the teacher should check if the data contains evidence that at some angle the light did not escape from the block of glass, and whether any student reports this observation. If not then the students should be instructed to check this, and discuss why they failed to discover this phenomenon. 
Possible questions: 
