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From radio waves to gamma rays

Science · Waves, Light & Sound · ages 15-16

Name ______________________ Date ____________

How do the speeds of different EM bands compare in empty space?
- Radio is fastest and gamma is slowest.
- Gamma is fastest and radio is slowest.
- All travel at the same speed.
Which list gives the usual seven-band spectrum order of rising frequency?
- Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma
- Gamma, X-ray, ultraviolet, visible, infrared, microwave, radio
- Visible, radio, gamma, microwave, X-ray, infrared, ultraviolet
Which statement about ionising EM radiation is accurate?
- Only radio, microwave and infrared photons can remove electrons from atoms.
- X-rays, gamma rays and sufficiently energetic UV can ionise atoms.
- Every ultraviolet photon removes electrons, while X-rays cannot remove them.
How does a microwave oven heat food?
- Food absorbs microwave energy, increasing its thermal energy.
- Water is ionised.
- Microwaves move faster than visible light and heat food by friction.
Why can X-rays produce an image of bones inside the body?
- Skin reflects nearly all X-rays, while bone reflects nearly none.
- Bone absorbs more X-rays than nearby soft tissue.
- Bone emits X-rays.
Gamma irradiation is used to sterilise suitable medical tools.
Circle one: True False
A germicidal UV-C lamp disinfects an exposed surface. Why does this use not mean that non-ionising UV is harmless to people?
- It kills microbes but cannot harm human skin or eyes.
- It harms microbes only after ionisation, so non-ionising UV cannot harm people.
- It damages genetic material and can also harm human skin and eyes.
A student says infrared cannot carry messages because heaters use it. Which reply explains why infrared can also work in a TV remote?
- The receiver detects sound signals.
- The receiver detects coded signals.
- The receiver detects heat patterns.

Answer key

For grown-ups. Fold this page away before handing over the rest.

From radio waves to gamma rays W1-mt_P_NXNSo1zQ-s1

All travel at the same speed. · All EM bands travel at the same speed in a vacuum, about 300,000,000 m/s. Different frequencies do not change that vacuum speed.
Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma · The usual increasing-frequency order starts with radio, passes through visible light, and ends with gamma rays.
X-rays, gamma rays and sufficiently energetic UV can ionise atoms. · Ionisation removes an electron from an atom. X-rays, gamma rays and sufficiently energetic UV can do this. Not all UV is ionising.
Food absorbs microwave energy, increasing its thermal energy. · Water molecules respond to the changing electric field. Food absorbs microwave energy, which becomes thermal energy. Ionisation is not required.
Bone absorbs more X-rays than nearby soft tissue. · Bone absorbs more X-rays than nearby soft tissue. Different amounts reach the detector, creating contrast in the image.
True · Controlled gamma irradiation damages microbes so they cannot reproduce. It can treat suitable medical tools through packaging.
It damages genetic material and can also harm human skin and eyes. · Germicidal UV-C can damage microbes' genetic material without requiring ionisation. UV-C can also harm human skin and eyes, so its useful application still needs exposure controls.
The receiver detects coded signals. · A remote sends a coded infrared signal to a receiver. The receiver detects the signal; the remote's communication role does not rely on heating the television.