Waves in a ripple tank — return questions

1. state / explain / calculate / describe

A loudspeaker plays a loud, low note. (a) State whether sound is a transverse or a longitudinal wave, and state one kind of wave that is modelled as the other kind. (b) A candle flame in front of the loudspeaker flickers towards it and away from it, but it is not blown away. Explain what this shows about what the sound transfers. (c) Another note from the loudspeaker has a frequency of 425 Hz and travels at 340 m/s. State what a frequency of 425 Hz means, and calculate the wavelength of this note. (d) A pupil models this sound with a slinky lying on a smooth floor. Describe how to move the end of the slinky, and explain why this models the sound.

(a) Transverse or longitudinal

(b) The candle flame

(c) The frequency and the wavelength

(d) A slinky model

2. state / explain / describe

You stand in a yard behind a tall building. A busy road runs past the front of the building, out of sight round the corner. (a) You can hear the traffic, though you cannot see it. State the name of the effect that lets the sound reach you round the corner of the building. (b) Supplement. The low rumble of a lorry engine has a wavelength of about 3 m; the hiss of its air brakes has a wavelength of about 5 cm. State which sound bends further round the corner, and explain why. (c) The traffic noise also bounces off a flat wall on the far side of the yard. State the name of this effect, and state one property of the sound that it leaves unchanged. (d) Describe how to show the effect in (a) with water waves in a ripple tank, using a single barrier. (e) Supplement. A marina is protected by two breakwaters with a gap 40 m wide between them, and sea waves 5.0 m long arrive at the gap. Change 1: the gap is narrowed to 30 m, for waves of the same length. Change 2: the gap stays 40 m wide, and a long swell with waves 15 m long arrives instead. State which change makes the waves spread out more beyond the gap, and explain why.

(a) Round the corner

(b) Supplement: rumble and hiss

(c) Off the far wall

(d) In a ripple tank

(e) Supplement: more spreading