1. What is the critical angle?

2. Complete the following sentences:

    a. If the angle of               is bigger than the               angle, the wave will reflect.

    b. If the               angle is bigger than the angle of incidence, the wave  will               .

    c. If the angle of               is equal to the critical angle, the wave will              at 90˚ to the          .

Endoscope

3. Explain how the endoscope works.

4. List three advantages of using optical fibres instead of copper wires for communication over long

    distances.