AS 2 Physics

• The law of conservation of energy states that the total amount of energy is constant in any process.
• wavefront? A wavefront is an imaginary surface that represents points in a wave that are in the same phase.
• period of a wave?

  The time it takes for one complete cycle of a wave.
• frequency of a wave?

  The number of oscillations ( or cycles) of a wave that occur in one second. measured in Hertz, Hz
• equation for frequency?

  Frequency = 1 / Period, or f = 1 / T
• wave equation?

  speed (c) = frequency (f) x wavelength (lamda) v = f(lamda)
• dispersion of waves is the spreading out of waves as they travel through a medium
• displacement of a wave?

  The distance an object moves from its equilibrium position when a wave passes through it.
• the amplitude of a wave is the maximum displacement from its undisturbed position
• energy is directly proportional to (amplitude)$^2$
• amplitude and energy equation is change in potential energy = mass x g x change in height
• the phase of a wave is the time taken for one complete wave to pass a point
• out of phase?

  When two waves are out of phase, it means they have a phase difference or are not synchronized.
• phase difference measured as an angle?


  One cycle is similar to one complete rotation, similar to 360°, there for half a cycle would be referred to as a pase difference of 180° (or $\pi$ radians )
• EM radio waves are used for radio and television broadcasting, mobile phone networks and satellite communications
• EM microwaves are used for satellite communication and radar.
• EM infrared radiation is used in remote controls, night vision goggles, and microwave ovens, there is a risk of burns
• EM visible waves are used for sight, photography, and TV. Can cause damage to retina.
• EM ultraviolet radiation can cause sunburn and skin cancer
• EM gamma rays are used for medical diagnosis and treatment, but also pose a significant health hazard due to their high energy.
• EM X-rays are used for medical imaging and airport security scanners. There is a risk of cancer from exposure to high levels of ionising radiation.
• shared qualities of EM waves? all travel in vacuum, travel at speed of light in vacuum, transverse waves, obey wave equation, heat up objects that absorb them, propagation of wave is rectilinear
• difference between electromagnetic waves and other types of waves? EM waves do not need a material medium to travel through, while others require one.
• Polarisation is splitting of a wave into two waves with opposite polarity.
• only transverse waves can be polarised
• Applications of Polarisation?

  Sunglasses, Photography, 3D cinema glasses
• Refraction is the bending of light as it passes from one medium to another.
• critical angle?


  The angle of incidence at which light is refracted at an angle of 90 degrees.
• what is a transverse wave?


  A wave that oscillates perpendicular to the direction of its propagation.
• what is a longitudinal wave?

  A wave that oscillates in the same direction as its propagation.
• refractive index?

  ratio of velocity of light in vacuum to its velocity in the material.
• refractive index of water?

  1.33
• refractive index of air?

  1.003 (approximately)
• refractive index of glass/perspex?

  1.5
• Snell’s law


  for a pair of media, the ratio of the sine of the incident angle to the sine of the refracted angle is a constant.

  
• equation of refractive index and speed of light 


  equation where both correlate

  
• Equation for refraction in two materials?

  Snell's Law

  
• Equation for critical angle?


  Snell's Law

  
• A fibre optic consists of a core of glass or plastic surrounded by a cladding of plastic or glass (lower refractive index)
• How does light travel along a fibre optic?

  Total internal reflection.