A student determines the speed of a wavefront on the surface of water. The student fills a plate with water and uses a dropping pipette to let one drop of water fall into the centre of the plate as shown in Fig. 1.1. [Figure 1.1] The wavefront that is produced travels outwards to the rim of the plate and then reflects back to the centre.

1. (a)Fig. 1.2 shows a scale marked on the side of the dropping pipette. [Figure 1.2] Describe the technique the student uses to put 1.0cm³ of water into the dropping pipette.[3]
2. (b)(i)The student observes the wavefront travel outwards from the centre of the plate and then reflect from the rim back to the centre. Fig. 1.3 is a side view of the wavefront as it spreads out across the diameter D of the plate. [Figure 1.3 (drawn to a scale of 1:2)] The student uses a stop-watch to measure the time t taken for the wavefront to travel outwards from the centre of the plate and then back to the centre. Fig. 1.4 shows three readings for time t. [Figure 1.4] Use the stop-watch readings in Fig. 1.4 to determine an accurate value for t. Show your working and give your answer to a suitable number of significant figures.[2]
3. (b)(ii)The speed of the wavefront can be calculated using the equation: speed = distance / time Fig. 1.3 is drawn to a scale of 1:2. It is half the size of the plate used in the experiment. Calculate the speed of the wavefront using your answer from (b)(i) and a measurement taken from Fig. 1.3.[2]
4. (c)(i)Identify two causes of uncertainty in this experiment.[2]
5. (c)(ii)Suggest one improvement that could be made to this experiment.[1]

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