Define transverse wave .

A transverse wave is a wave in which the particles oscillate perpendicular to the direction of the wave travel (and energy transfer).

Define longitudinal wave .

A longitudinal wave is a wave in which the particles oscillate parallel to the direction of the wave travel (and energy transfer).

Give two examples each of transverse and longitudinal waves.

Transverse: electromagnetic waves (e.g. radio, visible light, UV), vibrations on a guitar string. Longitudinal: sound waves, ultrasound waves.

True or False? Longitudinal waves can be polarised.

False. Only transverse waves can be polarised. Longitudinal waves oscillate parallel to the direction of travel, so there is no perpendicular plane of vibration to restrict.

Amplitude is the maximum displacement of a particle in the wave from its equilibrium position.

Phase difference is defined as how far the cycle of one point is compared to another .......... on the same wave.

Phase difference is defined as how far the cycle of one point is compared to another point on the same wave.

What is the phase difference between two points that are in phase, and between two points in antiphase?

In phase: 360° (2π radians). In antiphase: 180° (π radians).

What does it mean if one wave leads another by ¼ λ?

The leading wave's cycle is ahead of the other wave's; it reaches the same point in its oscillation a quarter of a wavelength earlier .

Define time period ( T ).

The time period is the time taken for one complete oscillation or cycle of a wave.

On a cathode-ray oscilloscope (CRO), what does each axis represent?

x-axis: time-base. y-axis: voltage (y-gain).

The time-base is how many seconds each division on a CRO screen represents, measured in s div -1 or s cm -1 .

The time period, T , is found by dividing the total time by the number of .......... shown on the screen.

The time period, T , is found by dividing the total time by the number of wavelengths shown on the screen.

True or False? Using only one wavelength on a CRO trace gives the most accurate value of the time period.

False. Using as many wavelengths as possible reduces the uncertainty in the calculated time period.

Why must time-base units be checked carefully before calculating frequency from a CRO trace?

The time-base can be given in different unit combinations (e.g. ms cm -1 , µs mm -1 ); the length unit must match the division measured, so unit conversions are often needed before calculating T and f .

For a wave travelling at constant speed, how does frequency change as wavelength increases?

As wavelength increases , frequency decreases (and vice versa), since speed = frequency × wavelength stays constant.

True or False? The symbol c should be used for the speed of any wave in the wave equation.

False. c is reserved for the speed of light (3 × 10 8 m s -1 ). Use v for the speed of any other wave, since only electromagnetic waves travel at c .

In the wave equation, as the wavelength decreases, the frequency .......... , provided the wave speed stays constant.

In the wave equation, as the wavelength decreases, the frequency increases , provided the wave speed stays constant.

Define compression (in a longitudinal wave).

A compression is a region of high pressure where particles are close together.

A rarefaction is a region of low pressure where particles are spread further apart.

On a displacement-position graph, what do crests and troughs represent?

Crests are the maximum positive displacements; troughs are the maximum negative displacements.

True or False? A displacement-time graph can always be used to tell whether a wave is transverse or longitudinal.

False. Both wave types can produce a graph that looks like a transverse wave. You must check whether the oscillation is perpendicular (transverse) or parallel (longitudinal) to the direction of travel.

In a ripple tank, a motorised straight-edged bar produces .......... waves, while a small dipper produces circular waves.

In a ripple tank, a motorised straight-edged bar produces plane (straight) waves, while a small dipper produces circular waves.

How is refraction investigated in a ripple tank?

A glass sheet is placed in the tank to decrease the water depth , producing a region where the wave travels at a different speed .

What does a decrease in the separation of wavefronts in a ripple tank indicate?

The wave is travelling more slowly .

Define wavefronts (as seen in a ripple tank).

Wavefronts are the bright bands seen on the screen below a ripple tank, corresponding to the wave crests .

For a spherical wave, the area used to calculate intensity is the surface area of a sphere, .......... .

For a spherical wave, the area used to calculate intensity is the surface area of a sphere, 4πr 2 .

A LevelPhysicsOCRFlashcards4. Electrons, Waves & PhotonsLongitudinal & Transverse Waves

Longitudinal & Transverse Waves (OCR A Level Physics): Flashcards

Exam code: H556

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FrontProgressive Waves: Longitudinal & Transverse
Define transverse wave.

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Cards in this collection (35)

Define transverse wave.
A transverse wave is a wave in which the particles oscillate perpendicular to the direction of the wave travel (and energy transfer).
Define longitudinal wave.
A longitudinal wave is a wave in which the particles oscillate parallel to the direction of the wave travel (and energy transfer).
Give two examples each of transverse and longitudinal waves.
Transverse: electromagnetic waves (e.g. radio, visible light, UV), vibrations on a guitar string.
Longitudinal: sound waves, ultrasound waves.
True or False?
Longitudinal waves can be polarised.
False.
Only transverse waves can be polarised. Longitudinal waves oscillate parallel to the direction of travel, so there is no perpendicular plane of vibration to restrict.
Define amplitude.
Amplitude is the maximum displacement of a particle in the wave from its equilibrium position.
Phase difference is defined as how far the cycle of one point is compared to another .......... on the same wave.
Phase difference is defined as how far the cycle of one point is compared to another point on the same wave.
What is the phase difference between two points that are in phase, and between two points in antiphase?
In phase: 360° (2π radians).
In antiphase: 180° (π radians).
What does it mean if one wave leads another by ¼ λ?
The leading wave's cycle is ahead of the other wave's; it reaches the same point in its oscillation a quarter of a wavelength earlier.
Define frequency.
Frequency is the number of complete oscillations of a wave per unit time; $f = \frac{1}{T}$ where T is the time period.
Define time period (T).
The time period is the time taken for one complete oscillation or cycle of a wave.
A wave has a time period of 4 ms. Calculate its frequency.
$f = \frac{1}{T} = \frac{1}{4 \times 10^{- 3}} = 250 Hz$
On a cathode-ray oscilloscope (CRO), what does each axis represent?
x-axis: time-base.
y-axis: voltage (y-gain).
Define time-base.
The time-base is how many seconds each division on a CRO screen represents, measured in s div^-1 or s cm^-1.
The time period, T, is found by dividing the total time by the number of .......... shown on the screen.
The time period, T, is found by dividing the total time by the number of wavelengths shown on the screen.
True or False?
Using only one wavelength on a CRO trace gives the most accurate value of the time period.
False.
Using as many wavelengths as possible reduces the uncertainty in the calculated time period.
Why must time-base units be checked carefully before calculating frequency from a CRO trace?
The time-base can be given in different unit combinations (e.g. ms cm^-1, µs mm^-1); the length unit must match the division measured, so unit conversions are often needed before calculating T and f.
Define the wave equation.
The wave equation links the speed, frequency and wavelength of a wave: $v = f λ$
For a wave travelling at constant speed, how does frequency change as wavelength increases?
As wavelength increases, frequency decreases (and vice versa), since speed = frequency × wavelength stays constant.
True or False?
The symbol c should be used for the speed of any wave in the wave equation.
False.
c is reserved for the speed of light (3 × 10⁸ m s^-1). Use v for the speed of any other wave, since only electromagnetic waves travel at c.
In the wave equation, as the wavelength decreases, the frequency .........., provided the wave speed stays constant.
In the wave equation, as the wavelength decreases, the frequency increases, provided the wave speed stays constant.
A wave travels at 340 m s^-1 with a frequency of 500 Hz. Calculate its wavelength.
$λ = \frac{v}{f} = \frac{340}{500} = 0.68 m$
Define compression (in a longitudinal wave).
A compression is a region of high pressure where particles are close together.
Define rarefaction.
A rarefaction is a region of low pressure where particles are spread further apart.
On a displacement-position graph, what do crests and troughs represent?
Crests are the maximum positive displacements; troughs are the maximum negative displacements.
True or False?
A displacement-time graph can always be used to tell whether a wave is transverse or longitudinal.
False.
Both wave types can produce a graph that looks like a transverse wave. You must check whether the oscillation is perpendicular (transverse) or parallel (longitudinal) to the direction of travel.
In a ripple tank, a motorised straight-edged bar produces .......... waves, while a small dipper produces circular waves.
In a ripple tank, a motorised straight-edged bar produces plane (straight) waves, while a small dipper produces circular waves.
How is refraction investigated in a ripple tank?
A glass sheet is placed in the tank to decrease the water depth, producing a region where the wave travels at a different speed.
What does a decrease in the separation of wavefronts in a ripple tank indicate?
The wave is travelling more slowly.
Define wavefronts (as seen in a ripple tank).
Wavefronts are the bright bands seen on the screen below a ripple tank, corresponding to the wave crests.
Define intensity (of a wave).
Intensity is defined as power per unit area: $I = \frac{P}{A}$ , measured in W m^-2.
How is the intensity of a wave related to its amplitude and frequency?
Intensity is proportional to the square of the amplitude and the square of the frequency: $I \propto A^{2} f^{2}$
If the amplitude of a wave is doubled, by what factor does its intensity increase?
By a factor of 4 (2²).
For a spherical wave, the area used to calculate intensity is the surface area of a sphere, ...........
For a spherical wave, the area used to calculate intensity is the surface area of a sphere, 4πr².
True or False?
Intensity decreases linearly with distance from a point source.
False.
Intensity follows an inverse square law: $I \propto \frac{1}{r^{2}}$ , so it decreases much more rapidly than linearly.
A point source's distance from an observer is doubled. By what factor does the intensity change?
It decreases by a factor of 4 (inverse square law: $I \propto 1 / r^{2}$ ).

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