Year 9 Science · Unit 4 · Lesson 8
Apply Worksheet
Learning Goals
Read the graph
The bar chart shows approximate wavelengths for the seven types of EM radiation. Study the chart, then answer the questions below.
Data: Wavelength ranges adapted from CSIRO EM spectrum reference, 2024
(a) Calculate the frequency of visible light with a wavelength of 500 nm. Use c = 3 × 10⁸ m/s. (Hint: convert nm to m first: 500 nm = 5 × 10⁻⁷ m.)
(b) Based on the graph, which EM wave type has the shortest wavelength? Explain why this means it carries the most energy per photon.
(c) Identify which EM wave type poses the greatest health risk to humans and explain why in terms of its wavelength and energy.
Real-world context
Australia consistently records some of the world’s highest UV indices. Across Queensland and much of northern Australia, the UV index regularly exceeds 11 (classified as “extreme”) during summer months. Australia has one of the highest rates of melanoma (skin cancer) in the world, leading to the widely promoted SunSmart campaign featuring the “slip, slop, slap, seek, slide” message.
(a) What type of EM radiation is UV, and where does it sit on the EM spectrum relative to visible light and X-rays? Include approximate frequency or wavelength values.
(b) Explain how UV radiation causes skin cancer at the cellular level. In your answer, refer to DNA damage and the role of ionising radiation.
(c) The SunSmart message includes “slip on a shirt, slop on sunscreen, slap on a hat.” For each of these three actions, explain the EM science that makes it effective at reducing UV exposure.
Wrap Up
In one sentence, what was the main idea of this lesson?