Question
Light and sound both travel as waves.
Draw a line from each statement to the correct term that describes it. One has been done for you 
Answer/Explanation
Answer:
change in direction of light when entering a medium – refraction
very high frequency sounds – ultrasound
a glass prism producing a spectrum – dispersion light spreading after passing through a narrow gap – diffraction
sound reflecting from a wall – echo
Question
A cruise ship has a firework display near a cliff as shown in Fig. 8.1.
A firework is sent into the air from the cruise ship. The firework explodes with a bright flash of light and a loud bang.
(a) People on a container ship see the flash before they hear the bang.
Explain why.
(b) The people on the container ship hear two bangs. They hear the second bang shortly after the first bang.
(i) Explain why they hear two bangs.
(ii) The speed of sound in air is 330 m / s. The firework explodes at a distance of 1.0 km from the container ship.
1. Calculate the time for the first bang to reach the people on the container ship.
time = ……………………………………………………………………………………………………..s
2. Estimate the time delay between hearing the first bang and second bang.
time = …………………………………………………………………………………………………………s
Answer/Explanation
Answer:
(a) indication of speeds / velocity
light quickest
(b)(i) echo /reflection (of sound)
from cliff
(b)(ii) speed = distance ÷ time in any recognised form
1000 ÷ 330
3.03 (s)
5–7 seconds