p6 waves

• frequency (f) - the number of oscillations per second (hertz)
• wavelength (λ) is the distance between two consecutive points on a wave
• period (T) - the time taken for one wavelength to pass
• T = 1/f (period = 1/frequency)
• v = f x λ (speed = frequency x wavelength)
• refraction is the change in direction of a wave passing from one medium to another caused by its change in speed
• away from normal - wave speed increases
• towards normal - wave speed decreases
• in a refraction frequency is constant
• angle of incidence = angle of reflection
• perfect black body - absorbs all radiation and does not reflect or emit any
• continuous EM spectrum order = gamma rays, x-rays, ultraviolet, light (visible), infrared, microwaves and radio waves
• water waves - transverse
• s-waves = transverse
• p waves = longitudinal
• gamma rays have the highest frequency and the shortest wavelength
• gamma rays - originate from changes in an atoms nucleus
• x-rays - ionising radiation which can cause mutations in cells and lead to cancer
• ultraviolet - increases risk of skin cancer
• infrared - heaters and infrared cameras ( fibre optic communications)
• microwaves - cooking food and comunications
• s-waves = solids only
• ultrasound waves are above the frequency of human hearing
• sound causes vibrations in the eardrum
• audible human hearing range = 20 Hz - 20kHz
• how to remember the EM spectrum - giant xylophones usually live in music rooms
• Alpha particles, beta particles and gamma rays are all types of ionising radiation.
• infrared is also used for cooking
• infrared and microwaves are both reflected by a shiny metal surface
• in a vacuum, em waves travel at 3 x 10^8m/s
• fluorescence is UV light energy being absorbed and re-emitted as visible light
• Gamma rays can be used to sterilise medical equipment and food. The rays can kill microorganisms without causing any other damage
• in reflection, the angle of incidence is always equal to the angle of reflection
• em waves are transverse waves
• a wave where oscillations are parallel to the direction of energy transfer is a longitudinal wave
• How x-rays work

  1. X-rays are fired at the patient
  2. X-rays are absorbed by materials which are very dense, like bones.
  3. X-rays are transmitted through materials which are not very dense, like lungs and intestines.
  4. The X-rays that pass through are detected by a detector plate to form an X-ray image
• the amplitude of a wave is the maximum displacement from the equilibrium position (the x-axis)
• microwaves and infrared waves have longer wavelengths than visible light
• x-rays and gamma rays have the shortest wavelengths and highest frequencies of all the electromagnetic waves
• the wavelength of the wave is the distance of one entire oscillation of that wave