Year 9 Science · Unit 4 · Lesson 10
Challenge Worksheet
Learning Goals
Read the graph — Noise levels in common environments
Study the bar chart showing typical decibel (dB) levels, then answer the questions below.
Data: Safe Work Australia (2022). Managing Noise and Preventing Hearing Loss at Work.
(a) Which environments in the graph exceed Safe Work Australia's 8-hour exposure limit of 85 dB? Name them.
(b) A student says "110 dB is exactly twice as loud as 55 dB." Explain why this statement is incorrect, using your knowledge of the decibel scale.
(c) Safe Work Australia states that at 91 dB, the maximum safe daily exposure is 2 hours. Using the pattern that every 3 dB increase halves safe exposure time, calculate the maximum safe daily exposure time at 94 dB and at 97 dB. Show your reasoning.
Find the mistake
Each statement below contains a scientific error from Lessons 6–9. In the answer column: (1) identify the error, (2) write the correct version, and (3) briefly explain why the error is wrong.
| Flawed statement | Identify the error, correct it, and explain |
|---|---|
| "Sound travels faster in air than in steel because air is less dense and the particles are spread out, so vibrations pass through easily." | |
| "Ultraviolet radiation has a lower frequency than infrared on the electromagnetic spectrum." | |
| "Refraction occurs because light reflects off the surface of the new medium and bounces at a different angle." | |
| "The ossicles (malleus, incus, and stapes) are found in the outer ear and help to direct sound waves into the ear canal." |
1. Fibre optic cables carry internet data across Australia using total internal reflection. Explain the conditions needed for total internal reflection and why glass fibre is particularly suited to this application.
2. A student claims that noise-induced hearing loss (NIHL) only affects people who work in very loud industries like mining or construction. Evaluate this claim using evidence from Lessons 6–9, including reference to dB levels and the structures of the ear that are damaged.
Wrap Up
In one sentence, what was the main idea of this lesson?