waves and electromagnetism

• deduce the practical for the ripple tank?

  1. adjust the height of the wooden rod to touch the water
  2. switch the lamp and motor and adjust until the waves can b observed
  3. measure the length of waves then divide by the number of waves to get the wavelength
  4. to record the frequency , count the number of waves and divide by 10
• deduce the practical to measure waves in a solid

  1. hold the metal rod at it's midpoint
  2. hit one end of the rod with a hammer
  3. hold a frequency measuring app at the end of the rod
  4. record the frequency and measure the length of the metal rod
  5. calculate the wavespeed
• Longitudinal wave

  A wave that moves parallel to the direction of energy transfer
• Transverse wave

  A wave that moves perpendicular to direction of energy transfer
• give some examples of transverse waves?

  ripples and light waves
• give some examples of longitudinal waves?

  sound waves , seismic waves
• How do you calculate time period?

  1/frequency
• How do you calculate frequency?

  wave speed/ wavelength
• How to calculate wave speed?

  frequency x wavelength
• How to calculate wavelength?

  wave speed/frequency
• how to convert m/s to km/s

  divide by 1000
• when white light is added which has all the wavelengths of the different colours of light, the different lights bend to different degrees , causing them to spread out.
• Give examples of ultrasound and infrasound?

  ultra -

  • Monitoring the growth and development of the fetus during pregnancy
  • checking the quality of products

  infra-

  sonar

  echolocation
• how does sound travel through the ear?

  • the sound particles enter the ear canal, which vibrate towards the ear drum
  • this then transmits the vibrations towards the ossicles
  • which travels to the coclea
  • this converts to electrical signals in the auditory nerves
  • which send a message to the brain that sound is being detected
• refraction?

  waves change direction when going from one medium to another , and when it enters a more dense materials , it bends towards the normal
• where does sound travel more quickly in ?

  it travels quicker in solids as there are more particles that are tightly packed , causing the waves to move faster
• glass to air?

  less than critical angle , away from the normal

  equal to critical angle , along the boundry

  more than critical angle , light refracts
• entering dense or less dense material?

  when entering a less dense material, it bends away from the normal

  when entering a more dense material, it bends towards the normal
• how does colour act in opaque material?

  objects appear to have a certain colour as all the other colours are being absorbed and this one is being refracted
• what is the practical for refraction?

  . place a glass box on paper and trace around it

  . pick a point the shine a ray of light towards it

  . draw a normal

  . measure the angle of incidence and the angle of refraction
• s-waves....?

  transverse waves that only travel through solids
• p-waves...?

  longtituinal waves that travel through liquids and solids
• what is the difference between concave and convex lenses?

  Concave: Diverging - refracts parallel rays of light inwards Convex: Converging - refracts parallel rays of light outwards
• what does a real image show compared to a virtual image?

  real image : light rays come together

  virtual image: light rays dont come together
• what is the pattern of the em spectrum?

  as the wavelength decreases , frequency increases
• dangers and uses of the em spectrum?

  Dangers: ionizing radiation, skin cancer.

  radiowaves : osscilations in electrical circuit

  Microwaves : domestic cooking communication

  IR: cooking , thermal imaging

  visable: vision , photography

  uv : water cleaning , security marking

  x-ray: medical scanners

  gamma rays : cancer treatment , sterilising food