5-WAC-04 Total Internal Reflection / Refraction

Outcomes

• Pupils understand the phenomenon of total internal reflection.
• Pupils understand the role of critical angle in TIR.
• Pupils recall uses of TIR.

Specification References

• 3.14 recall that light waves are transverse waves which can be reflected, refracted and diffracted
• 3.20 describe the role of total internal reflection in transmitting information along optical fibres and in prisms
• 3.21 recall the meaning of critical angle c

Main Body of Lesson

• Remind pupils how to set up rayboxes.
• Hand out rectangular blocks.
• Have pupils try to get a beam to "reflect inside the block". This shouldn't take long.
• Collect in rectangular blocks and replace with semicircular prisms.
• Have pupils line up ray of light so that angle of incidence is 0&degree; and then rotate through 90&degree;, maintaining the "exit" point of the ray as centre of the flat side of the prism (this makes more sense with a diagram).