Grade 8 · Science · Unit 2 of 9
Light & Radiation
Waves, the spectrum and how light behaves
What your child practises
Wavelength and frequency, the electromagnetic spectrum from radio waves to gamma rays and what each is used for, reflection, refraction and colour, and staying safe from UV radiation.
Saskatchewan Curriculum outcome: OP8.1, OP8.4 · light, its properties and electromagnetic radiation
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
Which type of radiation is used to take images of bones?
- infrared
- microwaves
- radio waves
- X-rays
Show answer
X-rays
Hint: X-rays pass through soft tissue but are blocked by bone.
Question 2
Why do we see white light split into colours in a prism?
- Light changes into sound.
- Different colours bend by different amounts when they refract.
- The prism makes new light.
- The prism adds paint.
Show answer
Different colours bend by different amounts when they refract.
Hint: Red bends least and violet bends most.
Question 3
Why is a red shirt red?
- It reflects all colours.
- It absorbs red light.
- It reflects red light and absorbs most other colours.
- It makes red light.
Show answer
It reflects red light and absorbs most other colours.
Hint: We see the colour of light that an object reflects.
Question 4
Put these types of electromagnetic radiation in order from the longest wavelength to the shortest.
- 🌈Visible light
- ☀️Ultraviolet
- 🍿Microwaves
- 🌡️Infrared
Show answer
Microwaves → Infrared → Visible light → Ultraviolet
Hint: The order is radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.
Question 5
Longer or shorter wavelength than visible light? Sort each radiation.
Sort into: 〰️ Longer than visible light · ⚡ Shorter than visible light
- ☢️gamma rays
- 🪫UV from a tanning lamp
- ☀️ultraviolet
- 📶Wi-Fi signals
- 🩻X-rays
- 🍿microwaves
- 📻radio waves
- 🌡️infrared
Show answer
〰️ Longer than visible light: Wi-Fi signals, microwaves, radio waves, infrared · ⚡ Shorter than visible light: gamma rays, UV from a tanning lamp, ultraviolet, X-rays
Hint: Radio waves, microwaves and infrared have longer wavelengths than visible light. Ultraviolet, X-rays and gamma rays have shorter wavelengths.
Question 6
Sound needs matter to travel. Light…
- cannot travel through space
- needs air
- needs water
- can travel through empty space
Show answer
can travel through empty space
Hint: That is how sunlight reaches Earth.