(a(i))[2]
State how the wave's speed, wavelength and frequency in the plastic block compare with those in air.
(a(ii))[1]
Show that the plastic has refractive index 1.4. Show your working.
(a(iii))[2]
Calculate the critical angle of the plastic.
(b(i))[2]
Extend ray P carefully until it reaches the other end of the fibre.
(b(ii))[2]
State two uses of optical fibres.