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11.5 Intensity

Quiz by John Farrant

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14 questions
Show answers
  • Q1
    What is the correct definition of the intensity of a wave?
    Power passing through a surface per metre squared
    Energy transferred to a surface per unit area
    Power passing through a surface per unit area
    Power per unit area
    30s
  • Q2
    What are the units of intensity?
    W m^2
    W m^-2
    Power per m^2
    J m^-2
    30s
  • Q3
    An astronaut is on the moon. He points a laser beam out into space. Will the intensity of the laser beam decrease with distance from the astronaut?
    No, because the waves from the laser are only in one direction and so don't spread out.
    Yes, because there are still a few particles in space that will absorb the energy.
    Yes, because, even though it is not a point source, the light waves will still spread out the further you get from a source.
    No, because space is a vacuum and so there are no particles to absorb the energy from the wave.
    30s
  • Q4
    If you know the intensity of a wave on a surface, how can you work out the power of the wave?
    Divide the intensity by the surface's area.
    Multiply the intensity by the surface's area.
    Divide the intensity by the exposure time
    Multiply the intensity by the exposure time
    30s
  • Q5
    What is the relationship between intensity and distance for a wave that comes from a point source?
    Intensity (in W/m^2) is proportional to distance (in m^2)
    Intensity (in W/m^2) is proportional to distance (in m) squared
    Intensity (in W/m^2) is inversely proportional to distance (in m^2)
    Intensity (in W/m^2) is inversely proportional to distance (in m) squared
    30s
  • Q6
    Why does music sound louder the closer you get to a speaker?
    Because the waves have spread out less
    Because less energy has been lost at this point.
    Because there are less particles between you and the speaker
    Because the waves have had less time to slow down
    30s
  • Q7
    What happens to a wave that comes from a point source?
    The wave spreads out evenly in all directions.
    The energy stays concentrated in one point.
    The source is pointing in a certain direction.
    Only one wave is ever produced.
    30s
  • Q8
    What is the equation to work out energy emitted using intensity?
    Intensity (in W/m^2) ÷ Area (in m^2) ÷ time (in s)
    Intensity (in W/m^2) x Area (in m^2) ÷ time (in s)
    Intensity (in W/m2) x Area (in m2) x time (in s)
    Intensity (in W/m^2) ÷ Area (in m^2) x time (in s)
    30s
  • Q9
    What is the relationship between intensity and amplitude?
    Intensity is inversely proportional to amplitude squared
    Intensity is proportional to amplitude squared
    Intensity squared is proportional to amplitude
    Intensity is directly proportional to amplitude
    30s
  • Q10
    Is intensity always proportional to the square of the amplitude?
    No, only for tranverse waves.
    No, only for positive amplitudes
    No, only for waves coming from a point source.
    Yes.
    30s
  • Q11
    If the amplitude of wave halves what happens to the intensity of the wave?
    It doubles
    It decreases by a factor of √2
    It quarters
    It halves
    30s
  • Q12
    If the intensity of a wave is doubled what happens to the amplitude of the wave?
    It increases by a factor of 4
    It increases by a factor of √2
    It increases by a factor of 2
    It decreases by a factor of √2
    30s
  • Q13
    The POWER of a wave that is 10m from its point source is 120W. What is the power of the wave at 20m?
    30W
    120W
    240W
    60W
    30s
  • Q14
    The INTENSITY of a wave that is 10m from its point source is 120W m-2. What is the intensity of the wave at 20m?
    60 W m^-2
    240 W m^-2
    120 W m^-2
    30 W m^-2
    30s

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