waves

• what are waves caused by?

  vibrations/disturbances
• what do all waves tranfer?

  energy
• transverse waves

  the wave moves perpendicular to the direction in which the particles are vibrating
• examples of transverse waves

  - water waves

  - all electromagnetic waves
• longitudinal waves

  the wave moves parallel to the direction in which the particles are vibrating
• example of longitudinal wave

  sound waves
• wavelength, λ

  - distance from a point on a wave to an identical point on the next wave

  - measured in metres, m
• amplitude

  - half the total height of the wave

  - measured in metres, m
• period, T

  - time taken for one full wave to pass a point

  - measured in seconds, s
• wave speed, v

  - distance travelled by a wavelength in one second

  - measured in metres per second, ms^-1
• frequency, f

  - number of waves passing a fixed point every second

  - measured in hertz, Hz
• diffraction

  the bending of waves around obstacles
• what does the amount of diffraction depend on?

  - the wavelength of the waves

  - the size of the gap through which they diffract
• ... waves diffract more than ... waves

  long, short
• waves diffract more through a ... gap than a ... gap

  narrow, wide
• what speed do em waves travel at?

  the speed of light (3.0 × 10^8 ms^-1)
• what are the em waves from low frequency/long wavelength to high frequency/short wavelength?

  - radio/ tv waves

  - microwaves

  - infrared

  - visible light

  - ultraviolet

  - x-rays

  - gamma rays
• source of radio/tv waves

  electronic circuit
• detectors of radio/tv waves

  - aerial

  - radio telescope
• applications of radio/tv waves

  - tv signals

  - bluetooth
• source of microwaves

  electronic circuit
• detector of microwaves

  aerial
• applications of microwaves

  - mobile phone

  - communication

  - heating food
• source of infrared

  any hot object (like a star)
• detectors of infrared

  - black-bulb

  - thermometer

  - photodiode
• applications of infrared

  - remote control

  - thermal imaging
• sources of visible light

  - LED

  - sun
• detectors of visible light

  - LDR

  - photographic film
• applications of visible light

  - laser eye surgery

  - lamp
• sources of ultraviolet

  - sun

  - uv discharge lamp
• detector of ultraviolet

  chemicals which fluoresce
• applications of ultraviolet

  - treating skin conditions

  - checking banknotes for security marks
• hazards of ultraviolet

  - sunburn

  - skin cancer
• source of x-rays

  electrons striking a metal target at high speed
• detector of x-rays

  photographic film
• applications of x-rays

  - detecting broken bones

  - radiotherapy
• hazard of x-rays

  cancer
• sources of gamma rays

  - uranium

  - plutonium
• detectors of gamma rays

  - photographic film

  - gm tube
• applications of gamma rays

  - radioactive tracers

  - radiotherapy