EM Spectrum

Question 1

List the EM spectrum, from highest frequency to lowest frequency.

Answer 1

Highest frequency Gamma radiation X-rays Ultraviolet Visible light Infra-red Microwaves Radio waves Lowest frequency

Question 2

What similarities do EM waves have?

Answer 2

All travel at the same speed All are transverse All can travel through a vacuum.

Question 3

What can gamma radiation be used for?

Answer 3

Medical tracers, removing cancer growths (radiotherapy), for sterilization of equipment and food.

Question 4

Why is infra-red radiation able to be measured by thermal imaging cameras to give an indication of temperature?

Answer 4

Infra-red radiation is emitted from anything with a temperature above absolute zero. Thermal cameras pick up anything in the wavelength range of infra-red. Humans have a temperature above absolute zero, so we emit infra-red radiation. Higher temperatures create higher frequency waves.

Question 5

What is the speed of light in a vacuum?

Answer 5

3x10⁸

Question 6

What reduces the speed of an electromagnetic wave?

Answer 6

Change of medium, e.g. human tissue is more dense than air, therefore the speed of the EM wave is reduced.

Question 7

What is a photon?

Answer 7

Waves can exist as both a wave and a particle. Photons are packets of energy (quanta)

Question 8

What is intensity?

Answer 8

Energy per second per unit area (Watts per metre squared)

Question 9

What is the relationship between frequency and intensity?

Answer 9

The higher the frequency of EM radiation, the higher the intensity of the wave.

Question 10

State the inverse square rule.

Answer 10

The distance of separation is proportional by the inverse square to intensity.

Question 11

What is the formula for the inverse square law?

Answer 11

Intensity is proportional to 1/(distance squared)