Home / iGCSE Physics (0625) 3.4 Sound Paper 3 -Exam Style Questions- New Syllabus

iGCSE Physics (0625) 3.4 Sound Paper 3 -Exam Style Questions- New Syllabus

IGCSE Physics (0625) Paper 3 - All Topics

Question

Fig. 6.1 shows some students near some rocky cliffs looking at a boat at sea. The students watch a firework display on the boat. One of the fireworks bursts and makes a loud sound.
(a) The students hear a loud sound from the firework and then they hear a quieter, similar sound.
State what causes the second quieter, similar sound.
(b) The time from when the students see the firework burst to when they hear the first, loud sound is 1.3 s.
Calculate the distance from the firework to the students.
Use the speed of sound in air = 340 m/s.

Most-appropriate topic codes (Cambridge IGCSE Physics 0625):

• Topic 3.4 — Sound (Parts (a), (b))

▶️ Answer/Explanation

(a)
For the correct answer:
(sound is) reflected (from cliff) OR echo (from cliff)

The first loud sound travels directly from the firework to the students. The second quieter sound is the echo, which occurs when the sound waves reflect off the rocky cliff and return to the students’ ears with less energy.

(b)
For the correct answer:
d = 442 m

The distance to the firework is found using the wave speed equation $v = \frac{d}{t}$, rearranged to $d = v \times t$. Given the speed of sound $v = 340\text{ m/s}$ and the time taken $t = 1.3\text{ s}$, the calculation is $d = 340 \times 1.3 = 442\text{ m}$.

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