waves

• a period is the time taken for a whole cycle to complete
• phase is a measurement of a position of a certain point along the wave cycle
• phase difference is the amount one wave lags behind another
• the equation for frequency is F=1/T
• the wave equation is $v=$$f\lambda$
• in longitudinal waves the vibrations are parallel to the direction of travel
• in transverse waves the oscillations are perpendicular to the direction of travel
• intensity is a measure of how much energy a wave is carrying
• the equation for intensity is I=P/A
• intensity is proportional to the amplitude squared
• types of EM waves

  1. Radio waves
  2. microwaves
  3. Infrared
  4. visible light
  5. UV
  6. xrays
  7. gamma rays
• refraction occurs when light passes a boundary between two different media. at the boundary the rays of light undergo a change of direction
• air-glass = light bends towards normal
• glass-air = light bends away from normal
• along normal = no change
• the refractive index is the property of a material which measures how much light slows down when passing through it
• the equation for refractive index is n=c/v
• high refractive index = optical dense
• n is always bigger than 1
• snells law relates the angle of incidence to the angle of refraction
• n1sin0=n2sin0 is the equation of snells law
• a critical angle is when the angle of refraction is at a right angle
• the angle for total internal reflection is sinC=1/n
• polarisation only occurs for transverse waves and occurs when vibrations are restricted in one direction
• diffraction is the spreading out of waves when they pass an obstruction
• the principle of superposition is when two or more waves with the same frequency arrived at a point, the result displacement is the sum of the displacements of the waves
• constructive is when the amplitude increases due to interference
• destructive is when the amplitude decreases due to interference
• two sources are coherent if they have the same wavelength, frequency and a fixed phase difference
• path difference is difference in distance travelled by 2 waves from their sources to the point where they meet
• the principle of superposition is that when two or more waves with the same frequency arrive at a point. the result displacement is the sum on the displacements
• a monochromatic wave is a wave of only one wavelength
• to carry out youngs double slit experiment

  1. Laser light is coherent and monochromatic
  2. the slits have to be the same size as the lazer light so that its diffracted. then the light from the slit acts like 2 coherent point sources
  3. you get a pattern of dark and light fringes. depending on wether constructive or destructive inteference is taking place
  4. use the equation x=λD/a
  5. To find the wavelength youll need to measure the fringe spacing
  6. the fringes are so tiny its easier to measure across several fringes then divide by the number of fringe spaces between them
• you can use the diffraction gratings to measure wavelength with the formula dsin0=nλ