em waves (topic 6)

Question 1

state one property that is the same for all electromagnetic waves

Answer 1

• all electromagnetic waves travel at the speed of light
• ability to travel through vacuum
• all electromagnetic waves are transverse

Question 2

describe one similarity and one difference between radio waves and gamma waves (2)

Answer 2

• both travel at the speed of light
• both transverse
• gamma has a shorter wavelength
• gamma has a higher frequency
• gamma has a higher energy

Question 3

complete the list of electromagnetic waves in order of increasing frequency

Answer 3

radio, microwaves, infrared, visible light, ultraviolet, x-ray, gamma

Question 4

the speed of light in a vacuum is

Answer 4

300,000,000 m/s

Question 5

state the name of two types of electromagnetic wave that are harmful and give their harmful effect

Answer 5

• infrared - skin burns
• ultraviolet - skin cancer
• gamma - mutation of cells

Question 6

explain why the doctor leaves the room but the patient is safe to have the X-ray (3)

Answer 6

• high exposure to x-rays can lead to cell mutations
• the patient has very few x-rays per year and so has a very low exposure
• the doctor would have a much higher exposure if they stayed in the room for every x-ray

Question 7

explain why the bones appear white but other areas appear darker from an x-ray (2)

Answer 7

• x-rays are absorbed by the bone, leaving the film white in these areas
• x-rays are able to penetrate tissue and be absorbed by the film

Question 8

49 MHz in Hz

Answer 8

4.9 x 10^7 Hz, multiply by 1 x 10^6

Question 9

explain why it is safer to use radio waves to send signals instead of gamma waves (2)

Answer 9

• radio waves are not harmful
• gamma is a high energy electromagnetic wave that can cause cell mutation

Question 10

explain what happens when the aerial of the remote control car absorbs a radio wave (2)

Answer 10

• an alternating current is induced
• with the same frequency as the radio wave

Question 11

describe one similarity and one difference between an electromagnetic wave and a sound wave (2)

Answer 11

• both transfer energy from one point to another without transferring matter
• sound is a longitudinal wave but electromagnetic waves are transverse
• sound requires a medium to travel through but electromagnetic waves can travel through a vacuum
• all electromagnetic waves travel at the speed of light but sound does not

Question 12

explain why microwaves are suitable for cooking food (3)

Answer 12

• microwaves are able to penetrate into food
• microwaves are absorbed by water molecules in the food
• causing them to vibrate and heat up the food

Question 13

explain how infrared is suitable for use in thermal imaging cameras (2)

Answer 13

• the higher the temperature of the object, the greater the amount of infrared radiation it emits
• a thermal imaging camera absorbs the infrared radiation and shows different colours to show differences in temperature levels

Question 14

Answer 14

Question 15

state one use of gamma radiation in the medical industry (2)

Answer 15

• sterilising medical equipment
• killing cancer cells

Question 16

state which two parts of the electromagnetic spectrum are used for long range communication

Answer 16

• radio waves
• microwaves

Question 17

explain what happens to the wavelength of electromagnetic waves as frequency increases (2)

Answer 17

• speed of light is the same for all electromagnetic waves
• as frequency increases, wavelength decreases