module 4 exam

• snells law is n1sin01=n2sin02
• air-glass=towards normal
• glass-air=away from normal
• the equation for refractive index is n=c/v
• to find the critical angle the equation is sinc=1/n
• investigation refraction and total internal reflection

  • independent variable = angle of incidence
  • dependent variable = angle of refraction
  • control variable = size of semicircular block, intensity of light
• method or investigating refraction and total internal reflection

  1. Place the semicircular block on the protractor and align 0 with the diameter
  2. direct light towards 0 and draw the normal
  3. use a pencil and ruler and trace the ray entering and leaving
  4. repeat this every 10 until 80 (which is the angle of incidence)
  5. the angle leaving the block Is the angle of refraction
  6. record the angle at which the angle of refraction is at 90
  7. repeat for the regtangular block
  8. use snells law to find n2
  9. use sinc=1/n2 to find the critical angle
  10. draw a graph of sin01/sin02 where the m=n
• stationary waves are caused by the superposition of two waves of the same frequency and amplitude travelling in opposite directions
• stationary waves store energy
• a node is where destructive interference happens which is where 2 waves cancel out causing no vibrations
• an antinode causes constructive interference which is where two waves add together creating a maximum amplitude
• to see a stationary wave you place a fine powder inside the air column and place a loudspeaker at the open end. at certain frequencies the powder forms evenly spaced heaps along the tube showing where there is zero disturbances as a result of the nodes of the stationary wave
• the wave produced by a loudspeaker reflects at one end of a tube. this reflected wave with the same frequency overlaps the initial wave to create a stationary wave
• determining the speed of sound in air in a resonance tube variables:

  • IV=air level in the tube
  • DV=length of the air column in the tube where resonance occurs
  • CV=temp of the water, frequency of tuning fork
• determining the speed of sound in air in a resonance tube method

  1. fill up the beaker halfway with water
  2. place the tube inside the beaker so the water comes up a quarter of the way. the sides of the tube in the water acts as a closed end.
  3. strike the tuning fork above the open end of the tube
  4. slowly lower the tube into the water until the intensity of the sound is amplified
  5. when resonance is heard mark the water level with a rubber band and record this as L1
  6. then lower the water further until the next point of resonance and record this as L2
• resonance occurs when L=lambda/4 and 3lambda/4 then find the wavelength by using the equation lambda=2(L2-L1)

  then the speed of sound is calculated using the wave equation speed of sound=lambda x frequency