wave phenomena

• what are wavefronts

  lines joining all the points that oscillate in phase and are perpendicular to the direction of motion
• what are rays

  lines showing the direction of motion of the wave that are perpendicular to the wavefront
• what is the distance between wavefronts equal to

  the wavelength of the waves
• what is an experiment that demonstrates the diffraction of water waves

  ripple tanks
• what do ripple tanks show in terms of frequency and wavelength

  the higher the frequency, the shorter the wavelength
• what can waves do when they arrive at a boundary

  reflect, refract or transmit
• what is reflection

  A wave hits a boundary between two media and does not pass through, but instead bounces back to the original medium
• what does the law of reflection state

  The angle of incidence, i = The angle of reflection, r
• what happens to the frequency, wavelength and speed of a wave during reflection

  they all stay the same
• what is refraction

  A wave changes speed and direction at the boundary between two media
• what happens to the wave when entering a more dense medium

  it slows down
• what is transmission

  A wave passes through a substance
• what happens to the amplitude of a wave when it is transmitted

  the amplitude decreases
• what is diffraction

  he spreading out of waves when they pass an obstruction
• what happens to the amplitude of a wave when it is diffracted

  it is less than the incident wave as energy is distributed over a larger area
• what happens to the wave when passing a slit that is equal to or smaller than the wavelength

  the diffraction is more prominent
• what happens to the wave when passing a slit that is larger than the wavelength

  the diffraction is less prominent, less spread out
• what happens to the light rays when they pass from air to glass

  they bend towards the normal, the angle of incidence is greater than the angle of refraction
• what happens to the light rays when they pass from glass to air

  they behind away from the normal, angle of refraction is greater than the angle of incidence
• how do you calculate the refractive index of a medium 


  n = c / v
• what is snell's law

  n1 / n2 = sin2 / sin 1 = v2 / v1
• what is the more convenient way of presenting snell's law

  n1 x sin1 = n2 x sin2
• what is the critical angle

  The smallest angle of incidence of which the light ray can totally internally reflect
• what happens if the angle of incidence is smaller than the critical angle

  the refracted ray bends away from the normal
• what happens if the angle of incidence is equal to the critical angle

  the fractured ray lies along the boundary of the 2 materials
• what happens if the angle if incidence is greater than the critical angle

  all light is reflected back into the material, total internal reflection
• how do you find the critical angle

  sin (critical angle) = n2 / n1
• what are the conditions for total internal reflection to occur

  the refractive index of the second material must be less than the index of the first

  the angle of incidence must be greater than the critical angle
• what is coherence

  when waves have a constant phase difference and the same frequency
• what is an example of a coherent light source

  laser lights
• what is an example of an incoherent light source

  filament lamps
• what happens to a coherent beam of light when it is incident on 2 narrow slits very close together

  diffraction occurs at each slit
• what happens to the diffracted waves from the beam of light in a double slit

  they interfere with each other
• where do bright fringed form from a double slit

  where the waves interfere constructively (i.e. crest meets a crest)
• where do dark fringes form from a double slit

  where the waves interfere destructively (i.e. crest meets a trough)
• what is superposition

  When two or more waves meet, the resultant displacement is the vector sum of the displacements of the individual waves 
• what is constructive interference

  Two or more waves superpose and have displacements in the same direction
• what is destructive interference

  Two or more waves superimpose and have displacements in opposite directions
• what happens when constructive interference occurs

  Two coherent waves combine by adding their displacements to create a resultant wave with a larger amplitude
• what happens when destructive interference occurs

  Two coherent waves combine by cancel out their displacements to create a resultant wave with a smaller amplitude