P5.2 - The Electromagnetic Spectrum

Question 1

Give properties of EM radiation.

Answer 1

• EM stands for electromagnetic.
• EM radiation is energy.
• EM radiation travels as a transverse wave.
• EM radiation doesn’t transfer matter - It is a
  transverse wave.
• The electric field, magnetic field and direction of
  energy transfer are all parallel to each other.
• EM radiation can travel in a vacuum as it doesn’t
  require particles.
• EM radiation is just different frequencies of light.

Question 2

What must happen in order to produce a wave of any kind?

Answer 2

In order to produce a wave of any kind, something must initially oscillate/vibrate.

Question 3

What is the speed of EM waves through a vacuum?

Answer 3

3.0 x 108m/s

Question 4

What is the electromagnetic spectrum?

Answer 4

The EM spectrum is a continuous range of all possible frequencies/wavelengths of EM radiation.

Question 5

What happens as the frequency of EM radiation increases?

Answer 5

• As the frequency of EM radiation increases, the
  energy of EM radiation increases.
• High energy EM radiation has small
  wavelengths.

Question 6

What is the amplitude of EM radiation a measure of?

Answer 6

Amplitude of EM radiation is a measure of the light

intensity (energy) - How much light is arriving in a given time over a given area.

Question 7

Give the sources of EM radiation in order of increasing frequency including the visible light spectrum.

Answer 7

Radio waves I Richard - Red
Microwaves I Of - Orange
Infrared I York - Yellow
Visible light ————– I Gave - Green
Ultraviolet I Battle - Blue
x-rays I In - Indigo
Gamma rays I Vain - Violet

Question 8

How are radio waves produced?

Answer 8

• An oscillating potential difference is applied
  across a wire.
• Electrons oscillate backwards and forwards at the
  same frequency.
• Produces oscillating electrostatic and magnetic
  fields.
• These fields travel and cut across an aerial.
• Electrons inside the aerial oscillate, producing an
  electric signal.

Question 9

What are the properties of radio waves?

Answer 9

• Easily pass through air and solids.
• Can be used for radio and tv signals.
• No hazards.

Question 10

What are the properties of microwaves?

Answer 10

• Easily pass through air and Earth’s atmosphere.
• Can be used for cooking food, mobile phones
  and satellites
• Can heat up water which is a possible risk to
  humans.

Question 11

What are the properties of infra-red waves?

Answer 11

• Pass through air and glass but stopped by solids.
• Can be used for night vision and remote controls.
• Absorbed by skin which causes it to heat up.

Question 12

What are properties of light?

Answer 12

• Passes through air and glass but is stopped by
  solids.
• Can be used to see cameras.
• Can have a very high amplitude and be very
  bright.

Question 13

What are the properties of ultraviolet waves?

Answer 13

• Moderately penetrates Earth’s atmosphere but
  can’t penetrate the skin.
• Can be used to produce vitamin D, detects bodily
  fluids and kills bacteria in water.
• Somewhat ionising which can damage skin cells
  leading to skin cancer.

Question 14

What are properties of X-Rays?

Answer 14

• Penetrates skin and thin metals but are stopped
  by bone and dense metals.
• Can be used for X-ray imaging and treatment of
  some cancers.
• Lightly ionising - likely to damage cells and give
  rise to cancer

Question 15

What are properties of gamma waves?

Answer 15

• Penetrates most material but is stopped by very
  thick lead.
• Can be used for treatment of cancer and the
  sterilisation of medical instruments.
• Quite ionising - likely to damage cells and give rise
  to cancer.

Question 16

Describe how infrared radiation is used for imaging.

Answer 16

• Thermal imaging cameras use infrared radiation
  to produce thermograms.
• A charged coupled device (CCD) absorbs the
  infrared radiation and displays it as visible
  colour.
• Different colours of visible light are used to
  indicate the different intensities of infrared
  radiation.
• The hotter a certain part of a medium, the more
  infrared light it will emit.

Question 17

Describe how X-ray radiation is used for imaging.

Answer 17

• X-rays produce images by showing contrast
  (differences in shades) between two media.
• In hospitals, X-rays are used to irradiate a person’s
  body.
• X-rays will pass through soft tissue (low density
  medium) but are absorbed by bone (high density
  medium) .
• X-rays that pass through the body, darken
  photographic film.
• The film remains white where X-rays were
  absorbed by the body and didn’t reach the film.

Question 18

Describe how gamma radiation is used for imaging.

Answer 18

• A radioactive tracer is a radioactive compound
  of an element.
• Radioactive tracers will (usually) emit gamma
  radiation.
• Radioactive tracers are ingested by/injected
  into a patient and quickly enter the bloodstream
  and organs.
• The intensity of the gamma radiation being
  emitted is monitored outside by a camera.
• Where there is poor blood flow inside the body,
  less gamma radiation will be emitted there, and
  this indicates a possible health problem.