13 Electromagnetic Spectrum 2021

A student is asked to give two uses of four different types of electromagnetic radiation.

In which row are both the uses correct?

• radio - sterilising medical equipment, mobile phone masts

• microwaves - mobile phones, sterilising medical equipment

• infrared - remote controllers, intruder alarms

• X-rays - security in airports, intruder alarms

The diagram shows typical wavelengths (in metres) of radio waves, microwaves and X-rays in the electromagnetic spectrum.

In which region are the waves used in TV remote controllers found?

• 8.0 ms

• 16 ms

• 8.0 s

• 16 s

• 1 and 3

• 1 only

• 2 and 3

• 2 only

Which row correctly describes what happens to the frequency and to the speed of electromagnetic waves as we move through the spectrum from γ-rays to radio waves?

• Frequency decreases, speed in a vacuum increases

• Frequency decreases, speed in a vacuum remains the same

• Frequency increases, speed in a vacuum decreases

• Frequency increases, speed in a vacuum remains the same

Thermal radiation is part of the electromagnetic spectrum. What is the name of this region of the spectrum?

• Gamma rays

• Infrared rays

• Ultraviolet rays

• Visible light rays

Which row gives the approximate speeds at which ultraviolet waves travel in air and in a vacuum?