topic 4

• What is the amplitude of a wave?

  This is the distance form the rest position of a wave to the crest(top) or trough (bottom).
• What is the wavelength?

  the distance between corresponding points on adjacent waves
• What is the frequency?


  number of waves that pass a point per second
• What is the period of a wave?

  The amount of time it takes for a full cycle of the wave
• What is the formula for the period?

  1/frequency
• What is a transverse wave?

  waves in which the particles vibrate in an up and down motion, perpendicular to the direction the wave is travelling
• What is a longitudinal wave?

  The wave energy moves parallel to the direction of the vibration. Particles are needed
• What is the formula for wave speed?

  wave speed = frequency x wavelength
• What is an oscilloscope?

  A device that can convert a sound signal into an electrical signal which it can display on a screen.
• How can you create water waves?

  using a signal generator attached to the dipper of a ripple tank
• What can happen to a wave at a boundary?

  absorption, transmission, reflection, refraction
• What happens when a light ray crosses from air into glass?

  - it will slow down, and bend towards the normal line
• WHat happens when a light ray crosses from glass into air?

  it will speed up, and bend away from the normal line
• What is total internal reflection?

  the complete reflection of light by the inside surface of a medium
• What is the rule concerning angles and reflection?

  angle of incidence = angle of reflection
• Describe the journey of a sound wave into the ear

  eardrum vibrates, wave travels to ossicles (which amplify the vibrations), through the semi-circuar canal and to the cochlea, which turns the vibrations into electric signals to be passed to the brain through the auditory nerve
• What is infrasound?


  Sound waves with a frequency below 20Hz
• What is ultrasound?


  Sound waves beyond the range of human hearing - 20,000Hz
• What is range of frequencies humans can hear?

  20-20,000 Hz
• What are uses ultrasound?

  Kidney scans, to find kidney stones (which reflect ultrasound)

  Heart scans

  Foetus scans

  Sonar in boats
• What are seismic waves?

  vibrations that travel through Earth carrying the energy released during an earthquake
• What are P-waves?


  can travel through both solids & liquids, moves by a pushing/pulsing motion, arrives "1st" (primary waves)

  longitudinal

  faster than S-waves

  
• What do converging lens do?

  Brings together light rays. It is the fat lens.

  The principle focus (F) of this lens is where the rays hitting the the lens parallel to the axis all meet

  the power is positive
• What do diverging (concave) lens do?

  Bends lihgt rays outwards. It is the thinner lens

  THe principle focus (F) of this lens is the point where rays hitting the lens parallel to the axis appear to all come from.

  The power is negative
• What can you do to a lens to increase its power?

  increase its curvature
• List the EM spectrum from long to short wavelength.

  Radio, micro, infrared, visible light, ultraviolet, X-rays, gamma rays
• What is the speed of light (and all EM waves)?

  3 x 10^8 m/s
• What are the uses of radio waves?

  Broadcasting and communications

  TV, radio, Bluetooth
• What are the uses of microwaves?

  Cooking and satellite transmissions

  Phones/ mobile communication devices
• What are the uses of infrared?

  Heaters and night vision equipment

  TV remote controls

  Security equipment

  Optical fibres which transfer information
• What are the uses of ultraviolet?

  Fluorescent lamps

  Security pens to mark laptops/ personal items

  Bank notes and passports have special markings to distinguish them from fakes

  sterilising water by killing bacteria
• What are X-rays used for?

  medical imaging

  airport security scanners
• What are gamma rays used for?

  Sterilising food and medical equipment, cancer treatment
• What are the dangers of EM radiation?

  - X-rays, gamma rays (X and G have most penetration power) and ultraviolets are ionising, so can damage cells, and cause mutations leading to cancer

  - IR can cause burns if the skin gets too much exposure

  - microwaes can cause heating of cells, which can be dangerous

  - ultraviolet can also damage eyes and cause blindness
• When is temperature (due to radiation) constant?

  WHen absorbtion energy = energy emmitted
• Which surfaces are better emmitters (black, aluminium or white)?

  black. they also absorb more radiation
• When can total internal reflection occur?


  travelling through dense material towards less dense material, when angle of incidence is larger than critical angle
• What are S-waves?


  ONLY travels through solids, moves by a shearing motion (up & down) and causes the most damage, arrives "second"

  Slower

  transverse

  
• what is the symbol for a diverging lens (on a ray diagram)?

  
• What is the symbol for a converging lens (on a ray diagram)?