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12PHYSICS WAVES SAC
VICTORIAN CERTIFICATE OF EDUCATION
2017
NAME:_________________________
TEACHER: ________________________
PHYSICS
School Assessed Coursework: Test
Wave Model of Light
Reading Time: 10 minutes
Writing time: 60 minutes
QUESTION AND ANSWER BOOK


Section
Number of
questions
Number of questions
to be answered
Number of marks
A
6
6
32
Students are permitted to bring into the examination room: pens, pencils, highlighters,
erasers, sharpeners, rulers, up to two pages (one A4 sheet) of pre-written notes (typed
or handwritten) and one scientific calculator.
Students are NOT permitted to bring into the examination room: blank sheets of paper
and/or white out liquid/tape.
Materials Supplied
 Question and Answer book of 8 pages. A formula sheet.
Instructions
 Write your student name and teacher name in the space provided above on this
page.
 Unless otherwise indicated, the diagrams in this book are not drawn to scale.
 All written responses must be in English.
At the end of the examination
 Close your Question and Answer booklet and ensure your name and your teacher’s
name is clearly printed on the front cover.
Students are NOT permitted to bring mobile phones and/or any other unauthorised
electronic devices into the examination room.
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12PHYSICS WAVES SAC
Area of study – Wave Model for Light
Instructions
Answer all questions in the spaces provided. Use black or blue pen.
Where an answer box has a unit printed in it, give your answer in that unit.
You should take the value of g to be 9.8 m s-2.
Where answer boxes have been provided, write your final answer in the box.
In questions where more than one mark is available, appropriate working must be shown.
Unless otherwise indicated, diagrams are not drawn to scale.
Question 1 (9 marks)
The following graph shows the displacement of a Nitrogen molecule in the air as a sound wave passes
through it at 340 m s-1.
Displacement (mm)
3.0
time (ms)
2.0
4.0
-3.0
a.
State the amplitude of the sound wave.
1 mark
3 .0 mm
b.
Find the frequency of the sound wave.
1 mark
1
T
________________________________________________________________________________
f 
4 103
T
1.5
1
________________________________________________________________________________
f 
3
T  2.667 10 s
2.667 103
________________________________________________________________________________
f  375 Hz
375 Hz
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12PHYSICS WAVES SAC
c.
Calculate the wavelength of the sound wave.
1 mark
vf
________________________________________________________________________________
340    375
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  0.91 m
0.91 m
d.
Is the wave Longitudinal or Transverse.
1 mark
Longitudinal
e.
Will the sound wave diffract if it travels through an aperture of 1.0 m. Explain your answer
and include a calculation.
3 marks
________________________________________________________________________________
________________________________________________________________________________

 A wave will significantly diffract if the ratio
1
w
________________________________________________________________________________
0.91
 Since
 0.91  1
1
________________________________________________________________________________
 The sound wave will diffract as it exits the 1.0 m aperture.
________________________________________________________________________________
________________________________________________________________________________
A student is moving towards the source of the sound wave.
f.
Describe how the period of sound wave as measured by the student compares to period of
the sound wave as measured by a stationary observer.
 The frequency of the sound wave measured by the student would be
________________________________________________________________________________
increased, in accordance with the Doppler Effect.
 As the period is inversely proportional to the frequency, the period of the
________________________________________________________________________________
sound wave will have decreased.
________________________________________________________________________________
________________________________________________________________________________
2 marks
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12PHYSICS WAVES SAC
Question 2 (3 marks)
Consider a red laser produces a wavelength of 650 nm.
a.
Calculate the frequency of the light produced by the laser.
1 mark
________________________________________________________________________________
cf
________________________________________________________________________________
3 108  650 109  f
________________________________________________________________________________
 f  4.6 1014 Hz
________________________________________________________________________________
4.6 × 104 Hz
b.
Compare the wavelength and speed of the laser light to that of infrared light.
________________________________________________________________________________
 Infrared  Laser
________________________________________________________________________________
 cInfrared  cLaser  3 108 m s 1
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
2 marks
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12PHYSICS WAVES SAC
Question 3 (8 marks)
Consider a green laser light travelling from water into air at an angle of 52o to the boundary.
Air (n = 1.0)
52o
Water (n = 1.3)
a.
b.
On the diagram above, draw a ray to illustrate the direction and angle of light exiting the
water.
1 mark
Calculate the angle to the normal the light exits the water.
2 marks
________________________________________________________________________________
i  90  52
ni  sin i  nr  sin  r
________________________________________________________________________________
1.3  sin  38   1 sin  r
i  38
________________________________________________________________________________
 r  sin 1 1.3  sin  38  
________________________________________________________________________________
  40.5
r
________________________________________________________________________________
40.5 o
c.
Calculate the critical angle and explain what happens if the critical angle is surpassed by
the incident light.
3 marks
ni  sin  c  nr  sin  90 
________________________________________________________________________________
________________________________________________________________________________
1.3  sin c  11
________________________________________________________________________________
 1 

 1.3 
________________________________________________________________________________
 c  sin 1 
 c  50.3
________________________________________________________________________________
50.3 o
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12PHYSICS WAVES SAC
d.
Calculate the speed of the green light when it is travelling in the water.
2 marks
________________________________________________________________________________
ni  vi  nr  vr
________________________________________________________________________________
8
1.3  vi  1 3 10
________________________________________________________________________________
3 108
1.3
________________________________________________________________________________
vi 
1
vi  2.3 10 m s
________________________________________________________________________________
8
2.3 × 108 m s-1
Question 4 (6 marks)
James points a green laser with a frequency of 5.55 × 1014 Hz at a double slit and observes the
pattern below on a screen.
C
a.
X
Calculate the wavelength of the green laser.
cf
________________________________________________________________________________
________________________________________________________________________________
3 108    5.55 1014
   5.41107 m
541 nm
1 mark
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12PHYSICS WAVES SAC
b.
Calculate the path difference from the slits to the third bright, X, from the central
maximum.
1 mark
PD  n
________________________________________________________________________________
7
PD  3  5.4110
________________________________________________________________________________
   1.62 10 m
________________________________________________________________________________
6
1620 nm
c.
James exchanges the laser with one of frequency 4.85 × 1014 Hz.
Describe the effect that this change will have on the pattern.
1 mark
________________________________________________________________________________
 Decreasing the frequency, increases the fringe spacing.
________________________________________________________________________________
d.
Explain how Young’s double slit experiment provides evidence for the wave nature of
light.
________________________________________________________________________________
 Young’s double slit experiment, shows light travelling through
the two slits causing an interference pattern of light and dark
________________________________________________________________________________
bands, which is characteristic of wave phenomena.
________________________________________________________________________________
 The light bands occur at regions of constructive interference
(where crests meet crests or troughs meet troughs) and the dark
________________________________________________________________________________
bands occur at regions of destructive interference (where crests
meet troughs).
________________________________________________________________________________
 The experiment doesn’t provide evidence for the particle model
because the particle model predicts that light should produce
________________________________________________________________________________
only two light bands directly in line with the two slits.
________________________________________________________________________________
3 marks
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12PHYSICS WAVES SAC
Question 5 (4 marks)
Consider a mix of blue and red light entering a diamond at angle of 15o to the normal.
Air
Diamond
Red
Blue
a.
On the Diagram draw and label the rays to represent both red and blue
2 marks
b.
Explain why red and blue light disperse in the diamond.
2 marks
________________________________________________________________________________
 The extent of diffraction is proportional to the frequency of the
________________________________________________________________________________
light.
 Since blue light has a higher frequency than red light, the blue
________________________________________________________________________________
light diffracts more than the red light.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 6 (2 marks)
Explain the how polarised sunglasses protect and improve the vision for a snow skier on a sunny
day.
___________________________________________________________________________________
 The reflected light from the snow is partially polarised.
___________________________________________________________________________________
 The polarised sunglasses block out some of the reflected light from the
snow, decreasing the glare and protecting the eyes.
___________________________________________________________________________________
___________________________________________________________________________________
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END OF OUTCOME 2