P5.2 - Electromagnetic Fields

Question 1

what angle do electromagnetic fields oscillate at (relative to the direction of the wave)?

Answer 1

90 degrees

Question 2

electromagnetic waves all have …….. ………..

Answer 2

the same velocity

Question 3

What speed do electromagnetic waves travel at? (and what is this the same as)

Answer 3

3 x 10 ^8 m/s

• same as speed of light

Question 4

name two sources of electromagnetic waves

Answer 4

microwave, sun

Question 5

what is the equation to calculate the frequency of a wave?

and what is the unit

Answer 5

wave speed
—————
wavelength

(Hz)

Question 6

State 2 uses of radio waves

Answer 6

• TV signals

- Used to transfer information (ie. between phones and satellites)

Question 7

State uses of micro waves,3

Answer 7

• to heat up food in the microwave
• communicate with satellites
• WiFi and bluetooth signals

Question 8

State uses of infrared waves, 4

Answer 8

• Remote controls
• used in optical fibres
• cooks food in oven or grill
• radiator transfers energy to thermal store

Question 9

State a use of visible light

Answer 9

• morse code in ships

- for photography

Question 10

State uses of ultraviolet waves, 5

Answer 10

• helps produce vitamin d
• bodily fluids glow in ultraviolet rays (ie. in crime scenes)
• to detect forged bank notes
• sterilises water (kills bacteria)
• can be used for suntans

Question 11

State uses of X-ray, 3

Answer 11

• used for X-rays
• can kill skin cancer or other skin cells
• used for airport security

Question 12

State uses of gamma rays, 4

Answer 12

• can kill cancer cells
• can kill bacteria in food
• can kill people
• can find leaks in underground pipes

Question 13

Are ultraviolet rays dangerous, and if so why?

Answer 13

YES

• can damage DNA in cells (grow very rapidly and cause skin cancer)
• if eyes exposed, cataracts can develop (make corneas cloudy)

Question 14

Are X-rays dangerous and if so why?

Answer 14

• can damage cells

- can cause cancer

Question 15

Are gamma rays dangerous and if so why?

Answer 15

• can damage cells in body

- can kill cells in body

Question 16

State a source of infrared rays

Answer 16

remote controls

Question 17

Name the group of the electromagnetic spectrum used to kill cancer cells.

Answer 17

gamma rays or x-rays

Question 18

Describe the nature of an electromagnetic wave

Answer 18

• oscillate at a right angle/90 degrees to the wave’s direction.
• wave pointing up = electric field
• wave pointing sideways = magnetic field
• it is a transverse wave

Question 19

Suggest a control variable for an experiment investigating various rays of the electromagnetic spectrum

Answer 19

• keep the same intensity of Electromagnetic radiation

Question 20

Describe why bones show up white on the X-ray film

Answer 20

• Bones absorb X-rays
• photographic film darkens when it absorbs X-rays
• X-rays pass through soft tissues (such as skin and muscle)

Question 21

When radiographers operate X-ray machines, they stand behind lead screens. The screens absorb X-rays and prevent the operators from being repeatedly exposed to radiation.
Why this is a necessary precaution.

Answer 21

X-rays / gamma rays can damage DNA / are harmful to cells

Question 22

what kind of waves are electromagnetic waves?

Answer 22

transverse waves

Question 23

what do electromagnetic waves transfer?

Answer 23

energy from sources to absorbers

Question 24

state examples of where electromagnetics transfer waves from sources to absorbers
(and describe what happens to the absorbers because of it)

Answer 24

microwave emits electromagnetic waves -> skin absorbs infrared waves

or “ -> food absorbs microwave radiation

• THEY BOTH HEAT UP

Question 25

what is the relationship between frequency and wavelength across the electromagnetic spectrum

Answer 25

the greater the frequency, the smaller the wavelength

Question 26

what are our eyes sensitive to?

Answer 26

only visible light, not absorbed by the atmosphere

Question 27

can electromagnet waves travel through a vacuum? | and why

Answer 27

yes! - as they are emitted from the sun and travel to the earth through SPACE - remember space is a vacuum

Question 28

describe the difference between a longitudinal and transverse wave

Answer 28

- in a longitudinal wave, oscillations occur parallel to the direction of energy transfer - in a transverse wave, oscillations occur perpendicular to the direction of energy transfer