Waves

• Transverse waves

  Waves where the oscillations of the wave are perpendicular to the direction of energy transfer
• Where can transverse waves travel in?

  Travel in solids and on the surface of the liquid but not inside liquids or gases
• What can some transverse waves travel in?

  Can move in a vacuum
• What is the highest point on a wave called?

  Peak or crest
• What is the lowest point of a wave?

  trough
• Examples of transverse waves

  -Ripples on the surface of water

  -Vibration in a guitar string

  -S-waves (a type of seismic wave)

  -Electromagnetic waves
• longitudinal wave


  Waves where the points along its length vibrate parallel to direction of energy transfer
• Where can longitudinal move in?

  Solids, liquids and gases
• Where can they not travel?

  Not move in a vacuum (no particles)
• example of longitudinal wave

  -Sound wave

  -P-waves (type of seismic wave)

  -Pressure waves caused by liquids or gases
• Longitudinal Wave Diagram

  
• How to measure speed of waves

  1) Two people stand a distance of around 100m appear

  2) The distance between them is measured using a trundle wheel

  3) One person has 2 wooden blocks, which they bang together above their head

  4) The 2nd person has a stopwatch which they start when they see the 1st person banging the block together and stops when they hear the sound

  5) Repeat this several times and average value taken for time

  6) The speed of sound can the be calculated using the equation - speed of sound= distance travelled by sound /time

  Method not very accurate because the time interval is very short
• Frequency


  Number of wave cycles in 1 second
• Wavelength


  Distance from a point on a wave to the equivalent point on the next wave
• What happens in reflection?

  When a wave bounces off the surface of a material
• What is colour?

  A property of visible light determined by its frequency
• What happens in refraction?

  A wave changes direction as it travel through a material because it changes speed
• What happens in absorption?

  The wave energy is transferred to an atom and the wave is stopped
• What happens in transmission?

  Waves passes through a material
• What are radio waves produced by?

  Oscillations in electrical circuits
• What can absorbed radio waves induce?

  Oscillation in electrical circuit
• Where do gamma rays come from?

  Changes in the atomic nucleus
• 3 ionising electromagnetic waves

  -Ultraviolet

  -X-rays

  -Gamma rays
• What is a radiation dose and its unit?

  A measure of the risk of harm from the body being exposed to radiation

  The risk depends on the total amount of radiation absorbed & how harmful the type of radiation is

  Measured in sieverts (Sv) or millisieverts (mSv)
• What does damage from radiation depend on?

  What part of the body is exposed, amount and type of radiation
• How are electromagnetic waves formed?

  By a proton or electron vibration which creates a changing magnetic field which then creates a changing electric field which then creates another changing magnetic field.

  
  

  Continues until the wave hits an object which absorbs its energy
• Amplitude


  Distance from point of zero disturbance to the point of maximum disturbance
• Electromagnetic waves in order of frequency

  -gamma

  -x-rays

  -ultraviolet

  -visible

  -infra-red

  -microwave

  -radio
• Electromagnetic wave in order of wavelength

  -radio

  -microwave

  -infra-red

  -visible

  -ultras-violet

  —x-rays

  -gamma rays
• Use of radio waves

  communication
• Use of microwaves

  Cooking

  Mobile phones

  Satellite
• Use of infrared waves

  Cooking

  Communications
• Use of visible light

  Optical fibres
• Use of ultraviolet

  Fluorescent lamps, tanning
• Use of x-rays

  Medical diagnosis
• Use of gamma rays

  Sterilising medical equipment and treating cancer
• Danger of radio waves

  Increased body temp
• Danger of microwaves

  Cause skin to burn
• Danger of infra-red

  -skin burns

  -extreme can cause skin cancer
• Danger of visible light

  Damage retina at back of eye