How many QCAA Physics Alternative Sequence questions cover Waves?

AusGrader has 89 QCAA Physics Alternative Sequence questions on Waves, all with instant AI grading and detailed marking feedback.

QCAA Physics Alternative Sequence Waves

15 sample questions with marking guides and sample answers

Q15

2020

QCAA

Paper 1

1 mark

Q15

1 mark

Identify which option best describes the type of wave behaviour displayed by particles of air as sound passes through them.

surface

transverse

longitudinal

electromagnetic

Reveal Answer

surface

Incorrect. Surface waves travel along the interface between two different media, such as water and air, whereas sound waves propagate through the bulk of the air.

transverse

Incorrect. In a transverse wave, particles oscillate perpendicular to the direction of wave travel, which does not describe how sound travels through a gas.

longitudinal

Correct Answer

Correct. Sound waves in air are longitudinal because the air particles vibrate parallel to the direction of wave propagation, creating alternating areas of compression and rarefaction.

electromagnetic

Incorrect. Electromagnetic waves consist of oscillating electric and magnetic fields and do not require a physical medium like air particles to propagate.

Q26

2022

QCAA

Paper 1

3 marks

Q26

3 marks

Two closed-ended pipe instruments of different lengths produce different natural frequencies.

Explain why the longer instrument produces a lower natural frequency.

Reveal Answer

Natural frequency is the frequency of a standing wave that can be formed and is dependent on the length of the pipe. This means a longer instrument allows standing waves of longer wavelength to form, which in turn corresponds to lower natural frequencies.

Marking Criteria

Descriptor	Marks
identifies that the natural frequency of the instrument is related to the frequency of standing waves inside the closed-ended pipe	1
explains the relationship between the length of the instrument and the wavelength of standing waves	1
explains the relationship between wavelength and frequency	1

2022

QCAA

Paper 2

3 marks

Contrast the properties of light and sound waves.

Reveal Answer

Sound waves are longitudinal in nature and require a medium to travel through. In contrast, light waves are transversal in nature and can travel in both a medium and vacuum.

In terms of the speed of these waves, light waves travel significantly faster than sound waves.

Marking Criteria

Descriptor	Marks
identifies differences between the nature of the waves	1
identifies differences between the relative speed of the waves	1
identifies differences between the requirement of a medium	1

Q32

2024

NESA

8 marks

Q32

8 marks

Many scientists have performed experiments to explore the interaction of light and matter.

Analyse how evidence from at least THREE such experiments has contributed to our understanding of physics.

Reveal Answer

Answers could include:

Reference to:

Black body radiation experiments and the development of quantum physics
Photoelectric experiments and the development of quantum physics
Spectroscopy experiments and the development of astrophysics and the atomic model
Polarisation experiments and the development of the wave nature of light
Interference and diffraction and the development of the wave model of light
Cosmic gamma rays and the development of theory of special relativity and/or the standard model.

Marking Criteria

Descriptor	Marks
Provides a detailed analysis using evidence from at least THREE experiments investigating the interaction of light and matter Provides a clear link between experimental evidence and greater understanding of physics	8
Provides analysis using evidence from experiments investigating the interaction of light and matter Provides a link between experimental evidence and greater understanding of physics	7
The student response meets all criteria of the 5-mark band, and additionally meets the majority of criteria in the 7-mark band.	6
Provides evidence from experiments investigating the interaction of light and matter Relates evidence to a greater understanding of physics	5
The student response meets all criteria of the 3-mark band, and additionally meets the majority of criteria in the 5-mark band.	4
Provides some information about evidence from an experiment AND/OR a link to physics	3
The student response meets all criteria of the 1-mark band, and additionally meets the majority of criteria in the 3-mark band.	2
Provides some relevant information	1
None of the above	0

Q23

2024

QCAA

Paper 1

4 marks

Q23

4 marks

A student set up a light box with a ray of light incident at an angle on a glass boundary. At the point of incidence, the student observed the light 'split' into two different rays.

Explain what happened to the ray of light at the air-glass boundary in terms of the angles.

Reveal Answer

Some of the light was refracted and some light was reflected. Refracted light passed through the glass and bent towards the normal, while reflected light bounced off the boundary at an angle equal to the incoming ray.

Marking Criteria

Descriptor	Marks
predicts refraction	1
explains that refracted ray bends towards the normal	1
predicts reflection	1
explains that reflected ray reflects at an angle equal to the incoming ray	1

Q16

2024

QCAA

Paper 1

1 mark

Q16

1 mark

A light wave of wavelength $555 \text{ nm}$ is shone from water onto glass. The refractive index of water is $1.33$ , and the refractive index of the glass is $1.50$ . Calculate the wavelength of the light in the glass.

$492 \text{ nm}$

$554 \text{ nm}$

$555 \text{ nm}$

$625 \text{ nm}$

Reveal Answer

$492 \text{ nm}$

Correct Answer

This is correct. The wavelength in the second medium is given by $\lambda_2 = \frac{n_1 \lambda_1}{n_2}$ . Substituting the values gives $\frac{1.33 \times 555 \text{ nm}}{1.50} = 492 \text{ nm}$ .

$554 \text{ nm}$

This is incorrect. This value does not correspond to the correct relationship between refractive indices and wavelengths, $n_1 \lambda_1 = n_2 \lambda_2$ .

$555 \text{ nm}$

This is incorrect. This is the wavelength of the light in water. The wavelength changes when light enters a medium with a different refractive index.

$625 \text{ nm}$

This is incorrect. This is the result of incorrectly multiplying the wavelength by $\frac{n_2}{n_1}$ instead of $\frac{n_1}{n_2}$ . Wavelength decreases when entering a medium with a higher refractive index.

2020

QCAA

Paper 1

1 mark

What is the frequency of light with a wavelength of 537 nm?

$5.59 \times 10^5$ Hz

$1.61 \times 10^{11}$ Hz

$5.59 \times 10^{14}$ Hz

$1.79 \times 10^{15}$ Hz

Reveal Answer

$5.59 \times 10^5$ Hz

This incorrect result comes from failing to convert the wavelength from nanometers to meters before dividing the speed of light by the wavelength.

$1.61 \times 10^{11}$ Hz

This value is incorrectly obtained by multiplying the speed of light by the wavelength, rather than dividing the speed of light by the wavelength.

$5.59 \times 10^{14}$ Hz

Correct Answer

Using the equation $\nu = \frac{c}{\lambda}$ , dividing the speed of light ( $3.00 \times 10^8$ m/s) by the wavelength in meters ( $537 \times 10^{-9}$ m) gives the correct frequency of $5.59 \times 10^{14}$ Hz.

$1.79 \times 10^{15}$ Hz

This incorrect result comes from dividing the wavelength by the speed of light ( $\frac{\lambda}{c}$ ) instead of dividing the speed of light by the wavelength ( $\frac{c}{\lambda}$ ).

2022

QCAA

Paper 2

2 marks

Describe how unpolarised light can be polarised.

Reveal Answer

Unpolarised light consists of waves travelling in planes that are not in alignment. When light is polarised, it passes through a filter that blocks all light waves except those in alignment with the direction of the filter.

Marking Criteria

Descriptor	Marks
describes unpolarised light	1
describes the role of a polarising filter	1

Q10

2022

VCAA

1 mark

Q10

1 mark

Which one of the following statements best describes an observation of the Doppler effect for sound?

a decrease in frequency received when a source of sound moves towards you

a decrease in frequency received when moving towards a stationary source of sound

an increase in frequency received when moving towards a stationary source of sound

a decrease in wavelength received when moving away from a stationary source of sound

Reveal Answer

a decrease in frequency received when a source of sound moves towards you

When a sound source moves towards you, the sound waves are compressed, resulting in an increase, not a decrease, in the observed frequency.

a decrease in frequency received when moving towards a stationary source of sound

Moving towards a stationary sound source causes you to encounter the sound waves more frequently, which increases rather than decreases the observed frequency.

an increase in frequency received when moving towards a stationary source of sound

Correct Answer

The Doppler effect dictates that relative motion towards a sound source causes the observer to intercept wavefronts at a higher rate, resulting in an increased observed frequency.

a decrease in wavelength received when moving away from a stationary source of sound

When moving away from a stationary source, the observed frequency decreases, which corresponds to an apparent increase in wavelength, not a decrease.

Q16

2022

VCAA

1 mark

Q16

1 mark

Which one of the following phenomena best demonstrates that light waves are transverse?

polarisation

interference

dispersion

diffraction

Reveal Answer

polarisation

Correct Answer

Polarisation restricts the oscillations of a wave to a single plane perpendicular to the direction of travel, a property unique to transverse waves. Longitudinal waves cannot be polarised because their oscillations are parallel to the direction of propagation.

interference

Interference is the superposition of waves to form a resultant wave. This phenomenon occurs in both transverse and longitudinal waves (like sound), so it does not prove light is transverse.

dispersion

Dispersion is the separation of light into different colors due to varying refractive indices for different frequencies. While it demonstrates wave properties, it does not specifically prove the wave is transverse.

diffraction

Diffraction is the bending of waves around obstacles or through gaps. Because both transverse and longitudinal waves exhibit diffraction, it cannot be used to prove light is transverse.

Q15

2022

QCAA

Paper 1

1 mark

Q15

1 mark

Which option is a property of mechanical waves?

requiring a medium to propagate

propagating at the speed of light in a vacuum

being produced by an oscillating electric charge

comprising mutually perpendicular electric and magnetic fields

Reveal Answer

requiring a medium to propagate

Correct Answer

Mechanical waves, such as sound or seismic waves, transfer energy through particle interactions and therefore require a physical medium (solid, liquid, or gas) to travel.

propagating at the speed of light in a vacuum

Mechanical waves cannot travel through a vacuum because they require matter to propagate; traveling at the speed of light in a vacuum is a property of electromagnetic waves.

being produced by an oscillating electric charge

Oscillating electric charges produce electromagnetic waves. Mechanical waves are instead produced by a physical disturbance or vibration in a material medium.

comprising mutually perpendicular electric and magnetic fields

This describes the structure of an electromagnetic wave. Mechanical waves consist of oscillating matter, not electric and magnetic fields.

Q13

2023

VCAA

1 mark

Q13

1 mark

A physics student hears a clap of thunder shortly after observing a flash of lightning.

Which one of the following statements best describes the sound associated with the clap of thunder and the visible light associated with the flash of lightning?

Both the sound and the visible light are examples of transverse waves.

Both the sound and the visible light are examples of longitudinal waves.

Sound is an example of a transverse wave and visible light is an example of a longitudinal wave.

Sound is an example of a longitudinal wave and visible light is an example of a transverse wave.

Reveal Answer

Both the sound and the visible light are examples of transverse waves.

Incorrect. While visible light is a transverse wave, sound is a longitudinal wave because it propagates through compressions and rarefactions in the air.

Both the sound and the visible light are examples of longitudinal waves.

Incorrect. While sound is a longitudinal wave, visible light is an electromagnetic wave, which is transverse because its fields oscillate perpendicular to the direction of travel.

Sound is an example of a transverse wave and visible light is an example of a longitudinal wave.

Incorrect. This option reverses the wave types. Sound requires particle oscillation parallel to propagation (longitudinal), while light consists of perpendicular oscillating fields (transverse).

Sound is an example of a longitudinal wave and visible light is an example of a transverse wave.

Correct Answer

Correct. Sound is a longitudinal wave because air particles oscillate parallel to the wave's direction, whereas visible light is a transverse wave because its electromagnetic fields oscillate perpendicular to its direction of travel.

2020

QCAA

Paper 2

4 marks

The intensity of monochromatic light is measured to be 36 W m $^{-2}$ at a distance, $r$ , from the source.

Calculate the intensity of the light at a distance that is three times further away (i.e. $3r$ ) from the source (to 1 decimal place).

Reveal Answer

$r_{new}=3\times r_{old}$

$I\propto \dfrac{1}{r^2}$

\begin{align*} I_{new}&\propto \dfrac{1}{r_{new}^2}\\ I_{new}&\propto \dfrac{1}{(3\times r_{old})^2}\\ I_{new}&\propto \dfrac{1}{9r_{old}^2}\\ I_{new}&\propto \dfrac{1}{9}\times \dfrac{1}{r_{old}^2}\\ I_{new}&=\dfrac{1}{9}\times I_{old}\\ I_{new}&=\dfrac{1}{9}\times 36=4.0\ \text{W m}^{-2} \end{align*}

New light intensity = 4.0 W m–2 (to 1 decimal place)

Marking Criteria

Descriptor	Marks
indicates understanding of the physical scenario in relation to the distance from the light source	1
indicates an understanding of the relationship between the intensity of light at a distance	1
provides pertinent mathematical operation/s correctly performed	1
arrives at a consequentially correct answer	1

Q29

2023

NESA

4 marks

Q29

4 marks

When light from an incandescent lamp is passed through a plane polarising filter, the intensity of the light is reduced.

Explain this phenomenon.

Reveal Answer

Light from an incandescent lamp is unpolarised.

A polarising filter absorbs the component of the electric field of the electromagnetic wave that are not parallel to the polarisation direction of the filter.

The intensity of the light would be reduced as only the parallel components will pass through the filter.

Marking Criteria

Descriptor	Marks
Relates the interaction between the filter and differing planes of oscillation of the electromagnetic waves to the reduction of light intensity	4
Relates the differing planes of polarisation of the light to the absorption of radiation by the polarising filter	3
Outlines a relevant feature of light from an incandescent lamp OR Outlines a feature of the interaction of electromagnetic radiation with a polarising filter	2
Provides some relevant information	1
None of the above	0

Q23

2020

QCAA

Paper 1

3 marks

Q23

3 marks

A light ray travelling through a piece of glass hits the interface between the glass and air. Calculate the smallest incident angle for total internal reflection to occur between these two media (to 1 decimal place). Assume the refractive index of the glass is 1.45 and the refractive index of air is 1.00.

Reveal Answer

For total internal reflection to occur, $r = 90^\circ$

\begin{align*} \frac{\sin i}{\sin r} &= \frac{n_2}{n_1}\\ \frac{\sin i}{\sin 90^\circ} &= \frac{1.00}{1.45}\\ \sin i &= \frac{1.00}{1.45} \times \sin 90^\circ\\ \sin i &= 0.690\\ i &= 43.6^\circ \end{align*}

Smallest incident angle = 43.6° (to 1 decimal place)

Marking Criteria

Descriptor	Marks
indicates an understanding of the physical scenario in relation to Snell's Law	1
provides pertinent mathematical operation/s correctly performed	1
arrives at a consequentially correct value	1

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