(a) Below shows the air pressure variation along a sound wave.

(i) On AB in the figure, mark one point of compression with a dot and the letter C and the next point of rarefaction with a dot and the letter R.

(ii) In terms of the wavelength, what is the distance along the wave between a compression and the next rarefaction?

(b) A sound wave travels through air at a speed of 340 m/s. Calculate the frequency of a sound wave of wavelength 1.3 m.

(a) Below shows the results of an experiment to find the critical angle for light in a semicircular glass block.

The ray of light PO hits the glass at O at an angle of incidence of 0°. Q is the centre of the straight side of the block.

(i) Measure the critical angle of the glass from the figure above

(ii) Explain what is meant by the critical angle of the light in the glass.

(b) Below figure shows another ray passing through the same block.

The speed of the light between W and Q is 3.0 × 10^{8}m/s. The speed of the light between Q and Y is 2.0 × 10^{8}m/s.

(i) State the speed of the light between Y and Z.

(ii) Write down an expression, in terms of the speeds of the light, that may be used to find the refractive index of the glass. Determine the value of the refractive index.

(iii) Explain why there is no change of direction of ray QY as it passes out of the glass.

(iv) What happens to the wavelength of the light as it passes out of the glass?

The figure below shows the diffraction of waves by a narrow gap.

P is a wavefront that has passed through the gap.

(a) On Fig above, draw three more wavefronts to the right of the gap.

(b) The waves travel towards the gap at a speed of 3 x 10^{8}m/s and have a frequency of 5 x 10^{14} Hz. Calculate the wavelength of these waves.

The figure below shows an optical fibre. XY is a ray of light passing along the fibre.

(a) On the figure, continue the ray XY until it passes Z.

(b) Explain why the ray does not leave the fibre at Y.

(c) The light in the optical fibre has a wavelength of 3.2 x 10^{–7} m and is travelling at a speed of 1.9 x 10^{8}m/s.

(i) Calculate the frequency of the light.

(ii) The speed of light in air is 3.0 x 10^{8}m/s.

Calculate the refractive index of the material from which the fibre is made.

The figure below shows plane waves passing through a gap in a barrier that is approximately equal to the wavelength of the waves.

(a) What is the name given to the wave property shown in the figure?

(b) In the space below, carefully draw the pattern that would be obtained if the gap were increased to six times the wavelength of the waves.

(c) The effect in the figure is often shown using water waves on the surface of a tank of water. These are transverse waves. Explain what is meant by a transverse wave.

In the figure below shows the path of a sound wave from a source X.

(a) State why a person standing at point Y hears an echo.

(b) The frequency of the sound wave leaving X is 400 Hz. State the frequency of the sound wave reaching Y.

(c) The speed of the sound wave leaving X is 330 m/s. Calculate the wavelength of these sound waves.

(d) Sound waves are longitudinal waves.

State what is meant by the term longitudinal.