Waves

• What is a progressive wave?

  A wave that transfers energy without material
• How do water waves behave?

  Water particles move up and down
• What is amplitude in a wave?

  Maximum displacement from equilibrium
• What is frequency measured in?

  Hertz (Hz)
• What does wavelength represent?

  Length of one whole oscillation
• What is the unit for wave speed?

  Metres per second (m/s)
• What does phase indicate in a wave?

  Position of a point on a wave cycle
• What is phase difference?

  How much one wave lags behind another
• What is the period of a wave?

  Time taken for one full oscillation
• When are two points on a wave in phase?

  When they have the same displacement and velocity
• What happens when two points are completely out of phase?

  They are an odd integer of half cycles apart
• How is wave speed calculated?

  Speed = frequency multiplied by wavelength
• How is frequency related to period?

  Frequency = 1 over the period
• What defines transverse waves?

  Particles oscillate at right angles to energy transfer
• What type of waves are electromagnetic waves?

  Transverse waves
• How can transverse waves be demonstrated?

  By shaking a slinky vertically
• What characterizes longitudinal waves?

  Particles oscillate parallel to energy transfer
• What is an example of a longitudinal wave?

  Sound waves
• What is a polarised wave?

  A wave oscillating in only one plane
• Why can only transverse waves be polarised?

  Because their oscillations are perpendicular to travel
• How do Polaroid sunglasses work?

  They block partially polarised light
• What is the principle of superposition of waves?

  Displacements of two waves combine as they pass

  
• What is constructive interference?

  When two waves have displacement in the same direction
• What is destructive interference?

  When one wave has positive and another negative displacement
• What is a stationary wave?

  A wave formed from two progressive waves superimposing

  
• What occurs at antinodes in a stationary wave?

  Regions of maximum amplitude are formed
• What occurs at nodes in a stationary wave?

  Regions of no displacement are formed
• How is the first harmonic defined?

  Lowest frequency with two nodes and one antinode
• How do you find the distance between adjacent nodes?

  It is half a wavelength
• How do you calculate the frequency of a stationary wave?

  Using the formula involving length, tension, and mass per unit length
• How do harmonics relate to the first harmonic frequency?

  Second harmonic is double the first frequency
• What is an example of stationary microwaves?

  Formed by reflecting a microwave beam
• How can stationary sound waves be demonstrated?

  Using a speaker in a closed glass tube
• What is path difference?

  Difference in distance travelled by two waves
• What characterizes a coherent light source?

  Same frequency, wavelength, and fixed phase difference
• What is Young's double slit experiment used to demonstrate?

  Interference of light from two sources

  
• What happens when light passes through two slits in Young's experiment?

  It forms a pattern of light and dark fringes

  
• What is the formula for fringe spacing in Young's experiment?

  w = $\frac{s \lambda}{D}$
• What occurs when using white light in diffraction experiments?

  Wider maxima and less intense pattern
• What safety precautions should be taken when using lasers?

  Wear goggles and avoid reflective surfaces