Year 9 Science · Unit 4 · Lesson 1
Apply Worksheet
Learning Goals
True or False? Fix the false ones
Circle T or F for each statement. If the statement is false, rewrite it correctly on the line below.
Electromagnetic waves need a medium such as air or water to travel through.
Correct it:
When a water wave passes, the water molecules move to the shore along with the wave.
Correct it:
Sound cannot travel through the vacuum of space between Earth and the Moon.
Correct it:
Seismic waves generated by an earthquake are a form of electromagnetic radiation.
Correct it:
Real-world context
On 22 February 2011, a magnitude 6.3 earthquake struck Christchurch, New Zealand. Seismic waves radiated outward through Earth's crust, causing widespread destruction. At the same time, cameras and satellites captured light images of the damage, and news broadcasts used radio waves to transmit footage around the world — including to Australian viewers watching on television.
(a) Why are seismic waves classified as mechanical waves? Use the definition of a mechanical wave in your answer.
(b) Light images and radio signals from Christchurch reached Australia within seconds. Explain why light and radio waves could travel this path when sound could not.
(c) What does the difference between seismic waves and radio waves tell us about the key distinction between mechanical and electromagnetic waves?
Wrap Up
In one sentence, what was the main idea of this lesson?