Define the principle of superposition .

When two or more waves with the same frequency arrive at a point, the resultant displacement is the sum of the displacements of each wave.

Why do superposing waves in these experiments often travel in opposite directions ?

Because they are reflected at a boundary.

In a microwave oven, the interference of microwaves creates a .......... inside the oven, which is used to heat food.

In a microwave oven, the interference of microwaves creates a standing wave inside the oven, which is used to heat food.

What two pieces of apparatus (other than a reflector) are typically used in a microwave superposition experiment?

Two microwave transmitters and a microwave detector .

True or False? A loud sound is heard where two loudspeakers' sound waves cancel each other out.

False. A loud sound is heard where the waves reinforce one another (constructive interference); a quiet or no sound is heard where they cancel out (destructive interference).

How does the frequency (colour) of light affect the diffraction pattern seen on the screen?

The distance between the maxima and minima varies with the frequency of the light.

What does the resultant wave represent when two waves are shown superposing on a graph?

The sum of the displacements of the individual waves at each point, shown as the black line on the diagram.

Under what conditions is complete constructive or destructive interference seen most clearly on a superposition graph?

When the two superposing waves have the same speed , frequency and amplitude .

True or False? Only transverse waves can be represented as superposing on a displacement graph.

False. Any two waves, whether transverse or longitudinal , can superpose.

In a graphical representation of superposition, the black line represents the .......... wave.

In a graphical representation of superposition, the black line represents the resultant wave.

Define coherent waves.

Waves with the same frequency and a constant phase difference .

Define path difference .

The difference in distance travelled by two waves from their sources to the point where they meet.

Define phase difference .

The difference in phase between two waves that arrive at the same point, given as an angle in radians or degrees.

What path difference condition produces constructive interference?

A path difference of n λ , an integer number of whole wavelengths ( n = 1, 2, 3...).

What path difference condition produces destructive interference?

A path difference of ( n + ½)λ , an integer number of whole wavelengths plus a half wavelength.

Constructive interference occurs when the phase difference is an .......... multiple of π.

Constructive interference occurs when the phase difference is an even multiple of π.

True or False? Laser light is an example of an incoherent light source.

False. Laser light is coherent; filament lamps produce incoherent light waves.

What happens to the resultant amplitude when two waves of the same frequency and amplitude superpose in anti-phase?

The resultant wave has no amplitude — the peaks of one wave line up with the troughs of the other (destructive interference).

Why can sound waves demonstrate two-source interference through compressions and rarefactions?

Because sound waves are longitudinal waves , made up of compressions and rarefactions.

What condition produces constructive interference between two sound waves?

When two compressions or two rarefactions line up, making the sound appear louder .

What condition produces destructive interference between two sound waves?

When a compression lines up with a rarefaction (and vice versa), making the sound quieter .

How is two-source interference of microwaves detected experimentally?

Using a moveable microwave detector .

For microwaves, destructive interference is detected in regions where the detector picks up .......... signal.

For microwaves, destructive interference is detected in regions where the detector picks up no signal.

True or False? Constructive interference of microwaves is detected where the detector picks up no signal.

False. Constructive interference is detected where the detector picks up a maximum amplitude signal; no signal indicates destructive interference.

What two conditions must the sources of two overlapping waves satisfy for an interference pattern to be observed?

They must be coherent (constant phase difference) and monochromatic (single wavelength).

Which order value corresponds to the central maximum in a double-slit interference pattern?

n = 0 ; n = 1 is one order either side, and so on.

In Young's double-slit experiment, how does light passing through the single slit produce two coherent sources at the double slits?

The monochromatic light diffracts at the single slit, producing two light sources at slits A and B that originate from the same primary source, so they are coherent .

The double-slit equation only applies when the slit separation, a , is .......... the slit-to-screen distance, D .

The double-slit equation only applies when the slit separation, a , is much smaller than ( a << D ) the slit-to-screen distance, D .

Define Huygens' wavelets .

Points on a wavefront that each act as a source of secondary waves, spreading out and travelling at the same speed as the source wave.

True or False? Newton's corpuscular theory of light successfully explained interference and diffraction.

False. Corpuscles could not explain interference or diffraction; this led to light being viewed as a wave instead.

What type of fringe is produced by constructive interference, and what type by destructive interference, in a double-slit pattern?

Constructive interference produces bright fringes (most intense in the middle); destructive interference produces dark fringes where no light is seen.

Define the resolution of the measuring equipment used in this practical.

Metre ruler = 1 mm; Vernier callipers = 0.01 mm.

In the Young's double-slit practical, what are the independent and dependent variables?

Independent variable: distance between the slits and the screen, D . Dependent variable: fringe width, w .

What two variables must be controlled in the Young's double-slit practical?

The laser wavelength , λ , and the slit separation , s .

True or False? Using a diffraction grating with fewer slits per mm reduces the percentage uncertainty in the wavelength calculation.

False. Using a grating with more lines per mm gives greater values of h , which lowers the percentage uncertainty.

What is the maximum permitted output power of the Class 2 laser used in this practical, and what key safety precaution must be taken?

Maximum output of no more than 1 mW ; laser beams must never be allowed to shine into anyone's eyes, and reflective surfaces should be removed from the room.

Define stationary wave .

A stationary wave is formed by the superposition of two waves of the same frequency and amplitude travelling in opposite directions , producing a wave pattern where the peaks and troughs do not move.

How does energy behave differently in stationary waves compared to progressive waves?

Stationary waves store energy, whereas progressive waves transfer energy.

Name three ways in which a stationary wave can be demonstrated experimentally.

A stretched string , microwaves (source and reflecting plate), and a column of air (with fine powder to show the pattern).

For a stationary wave to form in an air column, there must be a .......... at one end and a maxima at the end with the loudspeaker.

For a stationary wave to form in an air column, there must be a minima (node) at one end and a maxima at the end with the loudspeaker.

What three conditions must two overlapping waves satisfy in order to produce a stationary wave?

They must have the same speed , the same frequency (or wavelength), and a similar amplitude , while travelling in opposite directions .

Why does a node form where two waves overlap in a stationary wave?

At a node, the two waves are in anti-phase , causing destructive interference ; the waves cancel out and there is no vibration.

Why does an antinode form where two waves overlap in a stationary wave?

At an antinode, the two waves are in phase , causing constructive interference ; the waves add together and vibration is at maximum amplitude.

True or False? A stationary wave can be produced by two waves of different frequencies travelling in the same direction.

False. A stationary wave requires two waves of the same frequency and similar amplitude , travelling in opposite directions .

What do progressive and stationary waves have in common, in terms of the particles in the medium?

Both involve the oscillations (vibrations) of particles in the medium.

State three properties that particles have in both progressive and stationary waves.

Frequency , period of oscillation , and amplitude .

Both progressive and stationary waves can be described using the general .......... .

Both progressive and stationary waves can be described using the general wave equation .

A LevelPhysicsOCRFlashcards4. Electrons, Waves & PhotonsSuperposition & Stationary Waves

Superposition & Stationary Waves (OCR A Level Physics): Flashcards

Exam code: H556

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Define the principle of superposition.

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Cards in this collection (76)

Define the principle of superposition.
When two or more waves with the same frequency arrive at a point, the resultant displacement is the sum of the displacements of each wave.
Why do superposing waves in these experiments often travel in opposite directions?
Because they are reflected at a boundary.
Name the three types of wave commonly used to demonstrate superposition experimentally.
Sound, light and microwaves.
In a microwave oven, the interference of microwaves creates a .......... inside the oven, which is used to heat food.
In a microwave oven, the interference of microwaves creates a standing wave inside the oven, which is used to heat food.
What two pieces of apparatus (other than a reflector) are typically used in a microwave superposition experiment?
Two microwave transmitters and a microwave detector.
True or False?
A loud sound is heard where two loudspeakers' sound waves cancel each other out.
False.
A loud sound is heard where the waves reinforce one another (constructive interference); a quiet or no sound is heard where they cancel out (destructive interference).
What produces a microwave stationary wave when only one transmitter is used?
A microwave reflector.
How does the frequency (colour) of light affect the diffraction pattern seen on the screen?
The distance between the maxima and minima varies with the frequency of the light.
What does the resultant wave represent when two waves are shown superposing on a graph?
The sum of the displacements of the individual waves at each point, shown as the black line on the diagram.
Under what conditions is complete constructive or destructive interference seen most clearly on a superposition graph?
When the two superposing waves have the same speed, frequency and amplitude.
True or False?
Only transverse waves can be represented as superposing on a displacement graph.
False.
Any two waves, whether transverse or longitudinal, can superpose.
In a graphical representation of superposition, the black line represents the .......... wave.
In a graphical representation of superposition, the black line represents the resultant wave.
Define coherent waves.
Waves with the same frequency and a constant phase difference.
Define path difference.
The difference in distance travelled by two waves from their sources to the point where they meet.
Define phase difference.
The difference in phase between two waves that arrive at the same point, given as an angle in radians or degrees.
What path difference condition produces constructive interference?
A path difference of nλ, an integer number of whole wavelengths (n = 1, 2, 3...).
What path difference condition produces destructive interference?
A path difference of (n + ½)λ, an integer number of whole wavelengths plus a half wavelength.
Constructive interference occurs when the phase difference is an .......... multiple of π.
Constructive interference occurs when the phase difference is an even multiple of π.
True or False?
Laser light is an example of an incoherent light source.
False.
Laser light is coherent; filament lamps produce incoherent light waves.
What happens to the resultant amplitude when two waves of the same frequency and amplitude superpose in anti-phase?
The resultant wave has no amplitude — the peaks of one wave line up with the troughs of the other (destructive interference).
Why can sound waves demonstrate two-source interference through compressions and rarefactions?
Because sound waves are longitudinal waves, made up of compressions and rarefactions.
What condition produces constructive interference between two sound waves?
When two compressions or two rarefactions line up, making the sound appear louder.
What condition produces destructive interference between two sound waves?
When a compression lines up with a rarefaction (and vice versa), making the sound quieter.
Name a technology application that relies on destructive interference of sound waves.
Noise-cancelling headphones.
How is two-source interference of microwaves detected experimentally?
Using a moveable microwave detector.
For microwaves, destructive interference is detected in regions where the detector picks up .......... signal.
For microwaves, destructive interference is detected in regions where the detector picks up no signal.
True or False?
Constructive interference of microwaves is detected where the detector picks up no signal.
False.
Constructive interference is detected where the detector picks up a maximum amplitude signal; no signal indicates destructive interference.
What two conditions must the sources of two overlapping waves satisfy for an interference pattern to be observed?
They must be coherent (constant phase difference) and monochromatic (single wavelength).
Which order value corresponds to the central maximum in a double-slit interference pattern?
n = 0; n = 1 is one order either side, and so on.
In Young's double-slit experiment, how does light passing through the single slit produce two coherent sources at the double slits?
The monochromatic light diffracts at the single slit, producing two light sources at slits A and B that originate from the same primary source, so they are coherent.
The double-slit equation only applies when the slit separation, a, is .......... the slit-to-screen distance, D.
The double-slit equation only applies when the slit separation, a, is much smaller than (a << D) the slit-to-screen distance, D.
Define Huygens' wavelets.
Points on a wavefront that each act as a source of secondary waves, spreading out and travelling at the same speed as the source wave.
True or False?
Newton's corpuscular theory of light successfully explained interference and diffraction.
False.
Corpuscles could not explain interference or diffraction; this led to light being viewed as a wave instead.
What type of fringe is produced by constructive interference, and what type by destructive interference, in a double-slit pattern?
Constructive interference produces bright fringes (most intense in the middle); destructive interference produces dark fringes where no light is seen.
Define the resolution of the measuring equipment used in this practical.
Metre ruler = 1 mm; Vernier callipers = 0.01 mm.
In the Young's double-slit practical, what are the independent and dependent variables?
Independent variable: distance between the slits and the screen, D. Dependent variable: fringe width, w.
What two variables must be controlled in the Young's double-slit practical?
The laser wavelength, λ, and the slit separation, s.
How is the wavelength of the laser light calculated from a graph of w against D?
$λ = gradient \times s$ since the gradient of the w-D graph is equal to λ/s.
In the diffraction grating equation $n λ = d \sin θ$ , n represents the .......... of the diffraction pattern.
In the diffraction grating equation $n λ = d \sin θ$ , n represents the order of the diffraction pattern.
What is the accepted wavelength of light from a standard school red laser?
635 nm.
True or False?
Using a diffraction grating with fewer slits per mm reduces the percentage uncertainty in the wavelength calculation.
False.
Using a grating with more lines per mm gives greater values of h, which lowers the percentage uncertainty.
What is the maximum permitted output power of the Class 2 laser used in this practical, and what key safety precaution must be taken?
Maximum output of no more than 1 mW; laser beams must never be allowed to shine into anyone's eyes, and reflective surfaces should be removed from the room.
Define stationary wave.
A stationary wave is formed by the superposition of two waves of the same frequency and amplitude travelling in opposite directions, producing a wave pattern where the peaks and troughs do not move.
How does energy behave differently in stationary waves compared to progressive waves?
Stationary waves store energy, whereas progressive waves transfer energy.
Name three ways in which a stationary wave can be demonstrated experimentally.
A stretched string, microwaves (source and reflecting plate), and a column of air (with fine powder to show the pattern).
For a stationary wave to form in an air column, there must be a .......... at one end and a maxima at the end with the loudspeaker.
For a stationary wave to form in an air column, there must be a minima (node) at one end and a maxima at the end with the loudspeaker.
What three conditions must two overlapping waves satisfy in order to produce a stationary wave?
They must have the same speed, the same frequency (or wavelength), and a similar amplitude, while travelling in opposite directions.
Why does a node form where two waves overlap in a stationary wave?
At a node, the two waves are in anti-phase, causing destructive interference; the waves cancel out and there is no vibration.
Why does an antinode form where two waves overlap in a stationary wave?
At an antinode, the two waves are in phase, causing constructive interference; the waves add together and vibration is at maximum amplitude.
True or False?
A stationary wave can be produced by two waves of different frequencies travelling in the same direction.
False.
A stationary wave requires two waves of the same frequency and similar amplitude, travelling in opposite directions.
What do progressive and stationary waves have in common, in terms of the particles in the medium?
Both involve the oscillations (vibrations) of particles in the medium.
State three properties that particles have in both progressive and stationary waves.
Frequency, period of oscillation, and amplitude.
Both progressive and stationary waves can be described using the general ...........
Both progressive and stationary waves can be described using the general wave equation.
True or False?
Only progressive waves can be described using the general wave equation, since stationary waves behave in a completely different way.
False.
Both progressive and stationary waves can be described using the general wave equation, despite their differences.
Define node.
A node is a region on a stationary wave where there is no vibration (minimum disturbance).
Define antinode.
An antinode is a region on a stationary wave where the vibrations are at their maximum amplitude.
Do the nodes and antinodes of a stationary wave move along the string?
No. Nodes are fixed in position, and antinodes only move in the vertical direction — neither moves along the string.
How does the number of nodes between two points on a stationary wave determine their phase relationship?
An odd number of nodes between two points means they are out of phase; an even number of nodes means they are in phase.
The separation between adjacent nodes (or antinodes) on a stationary wave is equal to ...........
The separation between adjacent nodes (or antinodes) on a stationary wave is equal to λ/2.
How can the wavelength of a stationary wave be calculated from the distance between adjacent nodes?
λ = 2 × (distance between adjacent nodes), since adjacent nodes are separated by λ/2.
True or False?
Two points on a stationary wave separated by one node are in phase with each other.
False.
One node between two points is an odd number, so the points are out of phase.
What is the aim of the resonance tube experiment?
To calculate the speed of sound in air using a tuning fork and a tube of water.
In the resonance tube experiment, state the independent and dependent variables.
Independent variable: air level in the tube.
Dependent variable: length of the air column at resonance, L.
State two variables that must be controlled in the resonance tube experiment.
The temperature of the water and the frequency of the tuning fork.
Resonance occurs when the open tube length L is equal to .........., 3λ/4 and 5λ/4.
Resonance occurs when the open tube length L is equal to λ/4, 3λ/4 and 5λ/4.
How is the wavelength of sound calculated from two successive resonance lengths, L₁ and L₂?
λ = 2(L₂ − L₁).
How is the speed of sound calculated once the wavelength is known?
Using the wave equation, v = fλ, where f is the frequency of the tuning fork.
True or False?
The loudest sound in the resonance tube experiment occurs when the water level is at a node of the stationary wave.
False.
The loudest sound occurs at an antinode; the sound is quietest at a node.
State one precaution to reduce random error in the resonance tube experiment.
Submerge the tube slowly so the point of resonance is not missed, use a thin marker line, and repeat readings, since judging the loudest sound is subjective.
Define the fundamental mode (first harmonic).
The fundamental mode (first harmonic) is the simplest stationary wave pattern possible for a given system, corresponding to its lowest resonant frequency.
Describe the fundamental mode of a string fixed at both ends.
A single loop made up of two nodes and one antinode.
For a string fixed at both ends, the nth harmonic has n antinodes and .......... nodes.
For a string fixed at both ends, the nth harmonic has n antinodes and n + 1 nodes.
Describe the fundamental mode of vibration in an air column with only one open end.
A quarter wavelength, with one node and one antinode.
Describe the fundamental mode of vibration in an air column open at both ends.
One node and two antinodes.
For an air column closed at one end and open at the other, what equation relates the column length L to the wavelength λ and harmonic number n?
$L = \frac{n λ}{4}$
True or False?
The fundamental frequency and the first harmonic are two different resonant frequencies of a system.
False.
The fundamental frequency and the first harmonic (n = 1) are the same — the lowest resonant frequency of the system.

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