s

• incident ray and reflected ray

  Are equal
• If it changes speed

  It will refract
• When does a wave change speed

  Going through a different medium
• Denser medium

  The wave refracts towards the normal
• Less dense medium

  The wave refracts away from the normal
• If the angle of incidence is less than the critical angle...


  The light ray is refracted away from the normal.
• If the angle of incidence is equal to the critical angle...


  The emerging ray comes out along the surface.
• If the angle of incidence is greater than the critical angle...

  It will reflect
• What does a straight line gradient going through the origin mean

  X and Y are directly proportional
• Force and extension are

  directly proportional
• Limit of proportionality


  The limit for Hooke's law applied to the extension of a stretched spring
• Hooke's Law


  Extension is directly proportional to force until the spring reaches it's elastic limit
• elastic


  Returns to its original shape after distension or compression. Contains molecules of protein elastin that resemble coiled springs; molecules are cross-linked
• plastic


  able to be molded, altered, or bent but won't return to its original shape
• What is uncertainty?


  The amount of error your measurements might have
• How do you work out uncertainty

  (Max-min)/2
• Elasticity equation


  F=Ke
• The stiffer the spring...

  The steeper the gradient
• What does spring constant mean

  The stiffness of the spring
• elastic potential energy


  the energy of stretched or compressed objects
• elastic potential energy equation


  0.5 x spring constant x extension^2
• When do you use elastic potential energy equation

  Elastic deformation (stretching & compression)
• If the spring is not deformed, the work done on the spring and the elastic potential energy are...

  Equal
• plastic deformation


  permanent change in shape by bending and folding