Year 9 Science · Unit 4 · Lesson 5
Challenge Worksheet
Learning Goals
Comparing wavelengths across wave types
The bar chart below shows typical wavelengths for five different wave types. Study the chart carefully, then answer the questions. Note: bar heights use a relative scale because the values span many orders of magnitude.
Note: bar heights represent relative magnitude. Actual values shown above each bar. Seismic wave speed ≈3,000 m/s; sound in air ≈343 m/s; radio/light ≈3×10⁸ m/s; medical ultrasound in tissue ≈1,540 m/s.
(a) Using the wavelength values shown and the wave speeds given, rank the five wave types from highest to lowest frequency. Show at least one frequency calculation to support your ranking.
(b) Medical ultrasound (λ = 0.0015 m) is used to image soft tissue in the body. Explain why a very short wavelength is useful for medical imaging, and identify one wave property — from Lessons 1–4 — that makes ultrasound appropriate for this purpose.
(c) A radio wave has a wavelength of 3 m and travels at 3 × 10⁸ m/s. Calculate its frequency. Show your working.
Find the mistake
A student wrote this review essay on waves
"Waves transfer energy from place to place. Electromagnetic waves require a medium to travel through, which is why we can receive radio signals from the Moon. In a transverse wave, particles vibrate parallel to the wave direction, like the back-and-forth motion in a sound wave. When we measure the amplitude of a transverse wave, we measure from crest to trough. If you increase the frequency of a wave travelling in air, the wave will speed up to maintain the same wavelength."
1. This essay contains four scientific errors. Identify all four errors. List them clearly.
2. Choose two of the errors you identified. For each one, write the corrected version of that sentence and explain the scientific principle behind the correction.
Wrap Up
In one sentence, what was the main idea of this lesson?