1a. Two ducks are 8 m apart on a pond. Because of a wave, they both bob up and down for a period of 5 seconds. When one duck is at the crest of the wave, the other duck is at the bottom of a trough. The two ducks are always within a single cycle of the wave. Determine what the speed of the wave?

1b. The sound level 5.2 m away from a point sound source is measured at 110 dB. At what distance is the level 97 dB?

1c. Which of the following statements is true

Statement 1: The Doppler effect only exists for transverse waves.

Statement 2: When light is incident on a material where light waves travel slower, total internal reflection can occur if the angle of incidence is large enough.

Statement 3: Sound waves cannot be polarised because they are transverse waves.

Statement 4: The centre of the shadow of a circular opaque object is not always dark.

Statement 5: The diffraction of light in water droplets explains the existence of rainbows.