Electromagnetic waves

Question 1

properties of all electromagnetic waves: (3)

Answer 1

• transverse
• travel at the same speed through a vacuum (3x10^8)
• transfer energy as radiation from the source of the waves to an absorber

Question 2

what is the correlation between frequency, wavelength and energy between the waves of the electromagnetic spectrum? (2)

Answer 2

• waves with a very short wavelength, high frequency and high energy
• waves with a very long wavelength, low frequency and low energy

Question 3

name the electromagnetic waves and state their properties (generalised):

Answer 3

Radio waves, Microwaves, Infrared, Visible light, Ultra violet, X-ray, Gamma

long wave length short wavelength
low frequency ——————————————————————-> high frequency
low energy high energy

Question 4

which colours from the visible light spectrum have the highest and lowest frequency: (2)

Answer 4

• red light has the lowest frequencies of visible light

- violet light has the highest frequencies of visible light

Question 5

what does the behaviour of an electromagnetic wave depend on?

Answer 5

its frquency

Question 6

what does the increase of frequency mean for the electromagnetic waves?

Answer 6

EM waves become progressively more hazardous.

Question 7

how are radio waves transmitted?

why are they safe?

Answer 7

• through air

- they do not cause damage if absorbed by the human body

Question 8

how can radio waves be produced?

Answer 8

by oscillations in electrical circuits.

Question 9

describe the process of producing radio waves: (4)

Answer 9

• radio waves are absorbed by a conductor,
• they create an alternating current.
• this electrical current has the same frequency as the radio waves.
• information is coded into the wave before transmission, which can then be decoded when the wave is received.

Question 10

describe some usages of radio waves: (3)

Answer 10

• broadcasting
• communications
• satellite transmissions

Question 11

describe some usages of microwaves: (3)

Answer 11

• cooking
• communications
• satellite transmissions

Question 12

describe how microwaves work: (2)

Answer 12

• high frequency microwaves have frequencies which are easily absorbed by molecules in food.
• internal energy of the molecules increases when they absorb microwaves, which causes heating.

Question 13

why are microwaves appropriate for satellite communication? (2)

Answer 13

• pass easily through the atmosphere

- so they can pass between stations on Earth and satellites in orbit.

Question 14

describe the DANGERS of microwaves:

Answer 14

internal heating of body cells

Question 15

describe some usages of infrared waves: (6)

Answer 15

cooking, 
thermal imaging, 
short range communications, 
optical fibres, 
television remote controls 
security systems

Question 16

describe the DANGERS of infrared:

Answer 16

causes skin burns

Question 17

why is infrared appropriate for usage in electrical heaters and for cooking food? (3)

Answer 17

• it has frequencies which are absorbed by some chemical bonds.
• internal energy of the bonds increases when they absorb infrared light
• which causes heating. This makes infrared light useful for electrical heaters and for cooking food.

Question 18

why is infrared useful for detecting people in the dark? (3)

Answer 18

• all objects emit infrared light.
• human eye cannot see this light, but infrared cameras can detect it.
• this is ‘thermal imaging’

Question 19

describe some uses of visible light: (3)

Answer 19

vision, photography and illumination

Question 20

describe some uses of ultraviolet: (3)

Answer 20

fluorescent lamps,
detecting forged bank notes
disinfecting water

Question 21

describe the DANGERS of ultraviolet:

Answer 21

damage to surface cells and eyes, leading to skin cancer and eye conditions

Question 22

describe some usages of x-rays: (3)

Answer 22

observing the internal structure of objects,
airport security scanners
medical x-rays

Question 23

describe some usages of gamma rays: (2)

Answer 23

sterilising food and medical equipment,

detection of cancer and its treatment

Question 24

describe the DANGERS of x-rays and gamma rays:

Answer 24

both are ionising, which can cause the mutation of genes, leading to cancer

Question 25

what do all bodies do?

-irrespective of what?

Answer 25

• emit and absorb infrared radiation.

- their temperature

Question 26

what is the temperature of a body linked to?

Answer 26

balance between the amount of radiation absorbed and emitted

Question 27

describe the correlate between the rate of absorption and the temperature of a body: (3)

Answer 27

if greater than rate of emission = increasing body temperature

if equal to rate of emission = constant body temperature

if lower than rate of emission - decreasing body temperature