Waves Part 2

Question 1

What is a wave

Answer 1

• a wave is a transfer of energy without the transfer of matter
• waves can be used to transfer energy and information

Question 2

Transverse

Answer 2

• oscillations are perpendicular to the direction of wave travel

Question 3

Longitudinal

Answer 3

• oscillations are parallel to the direction of wave travel

Question 4

Wavelength

Answer 4

• distance between two identical points on a wave, measured in metres

Question 5

Frequency

Answer 5

• number of waves that pass a point per second, measured in hertz

Question 6

Amplitude

Answer 6

• maximum displacement from rest position. Larger amplitude = more energy

Question 7

Period

Answer 7

Time it takes for one complete wave

Question 8

Reflection

Answer 8

• when a wave bounces off a surface
• angle of incidence = angle of reflection
• smooth surfaces reflect better

Question 9

Refraction

Answer 9

• change in direction of a wave as it passes from one medium to another
• wave slows down in denser materials and bends towards the normal
• wave speeds up in less dense materials and bends away from the normal

Question 10

Transmission

Answer 10

• wave passes through a material

Question 11

Absorption

Answer 11

• wave energy is transferred into the material

Question 12

About the EM spectrum

Answer 12

• all EM waves are transverse
• all travel at the same speed through a vacuum
• arranged by increasing frequency and decreasing wavelength

Question 13

EM spectrum

Answer 13

• radio waves
• microwaves
• infrared (IR)
• visible light
• ultraviolet
• x-rays
• gamma rays

Question 14

Required practical: waves in a ripple tank (or springs)

Answer 14

• ripple tank: used to observe water wave behaviour like reflection and refraction
• method:
  1. Create waves using a vibrating dipper
  2. Use strobe light and ruler to measure wavelength
  3. Count waves per second (frequency)
  4. Calculate speed using v = f x wavelength

Question 15

Spring practical

Answer 15

• can be used to show longitudinal and transverse waves
• helps to visualise wave properties

Question 16

Radio waves

Answer 16

• longest wavelength and lowest frequency
• uses:
• broadcasting: transmit radio and TV signals over long distances
• communication: AM/FM radio, walkie-talkies
• Bluetooth/wifi/: short-range transmission of data
• advantages: can diffract around hills/buildings (good for long distance communications)
• can reflect off the ionosphere, allowing global broadcasts

Question 17

Microwaves

Answer 17

• uses:
• cooking: microwaves absorbed by water molecules, heating food from inside
• mobile phone signals: short-wavelength microwaves carry data
• satellite communication: travel through earth’s atmosphere; used in GPS and TV satellites
• dangers:
• can penetrate body tissue, causing internal heating and potential damage to cells
• prolonged exposure may be harmful

Question 18

Infrared

Answer 18

• uses:
• remote controls: send pulses to change channels/volume
• night vision: DTE test body heat (used by military police
• thermal imaging: see heat patterns in homes, engines, or medical scans
• cooking: grills and toasters emit IR radiation to heat food
• dangers:
• skin burns from too much exposure
• high-intensity IR can damage eyes

Question 20

Visible light

Answer 20

• uses:
• seeing: the only EM wave visible to humans
• photography and filming
• optical fibres: used n medical endoscopes and high-speed data transfer (light reflects inside cable)
• dangers:
• bright light: can damage retinas
• laser: can cause permanent eye injury

Question 21

Ultraviolet

Answer 21

• uses:
• fluorescent lamps: UV excites phosphor coating inside bulbs to emit visible light
• security marking; markings on money or documents glow under UV
• sterilisation: kills bacteria in water and medical equipment
• tanning beds: artificial UV exposure to darken skin
• dangers:
• skin can from prolonged exposure (mutates DNA)
• eye damage (can cause cataracts)
• sunburn and premature ageing of skin

Question 22

X-rays

Answer 22

• uses:
• medical imaging: x-rays pass through soft tissue but are absorbed by bones, producing an image
• airport security: scan luggage to see inside with ou opening
• industrial scanning: check welding seams, pipelines for cracks
• dangers:
• ionising radiation: can damage retinas damage or mutate DNA, leading to cancer
• used in controlled doses in medicine
• medical workers often wear lead aprons or stay behind barriers

Question 23

Gamma rays

Answer 23

• shortest wavelength, highest frequency, most energy
• uses:
• cancer treatment (radiotherapy): targets and kills cancer cells
• medical tracers: radioactive gamma-emitting isotopes used to track inside the body
• sterilisation of surgical instruments and food (kills microbes without heat)
• dangers:
• highly penetrating and ionising: can cause serious cell damage, mutations or leukaemia
• can pass through most materials - requires lead or concrete shielding

Question 24

Measuring radiation

Answer 24

• ionising radiation can be harmful
• sievert is the unit for radiation dose - how much biological damage radiation cases
• 1 sv = very high dose
• the higher the dose the greater the risk of cancer or cell mutation