A wavefront is a line joining all the points on a wave that oscillate in phase and are perpendicular to the direction of motion.

Define a ray in the context of waves.

A ray is a line showing the direction of motion and energy transfer of the wave, perpendicular to the wavefront .

True or False? A surface wave propagates in three dimensions.

False. A surface wave propagates in two dimensions.

What shape do wavefronts have for a surface wave?

The wavefronts for a surface wave are circular .

How are peaks and troughs represented in wavefront diagrams?

Peaks are represented with a darker line and troughs with a fainter line.

What is the distance between successive peak wavefronts called?

The distance between successive peak wavefronts is called the wavelength .

Define circular wavefronts .

Circular wavefronts are wavefronts that propagate in two dimensions, such as those on the surface of water.

What are spherical wavefronts?

Spherical wavefronts are wavefronts that propagate in three dimensions, such as those of sound or light waves.

State the relationship between wavefronts and rays.

Wavefronts are perpendicular to rays . Rays indicate the direction of motion and energy transfer of the wave.

Reflection is when a wave hits a boundary between two media and bounces back to the original medium without passing through.

True or False? During reflection, the frequency of the wave changes.

False. During reflection, the frequency, wavelength, and speed of the wave do not change.

Refraction is the change in direction of a wave when it passes through a boundary between mediums of different densities.

How does wave speed change when passing from a less dense to a more dense medium?

When a wave travels from a less dense medium to a more dense medium, its speed decreases .

What is the angle of incidence?

The angle of incidence is the angle between the incident ray and the normal line at the boundary between two media.

What happens to light when it travels from air to glass?

When light travels from air to glass, its speed decreases , its wavelength decreases , and it refracts towards the normal .

True or False? Refraction occurs without transmission when a wave passes through the boundary between two media.

False. Refraction always involves the transmission of the wave into the second medium.

Transmission is when a wave passes through a substance, and refraction is a specific type of transmission involving a change in direction.

What happens to the angle of refraction when light travels from a denser to a less dense medium?

When light travels from a denser to a less dense medium, the angle of refraction is greater than the angle of incidence, causing the light to bend away from the normal.

Diffraction is the spreading out of waves after they pass through a narrow gap or around an obstruction.

True or False? Diffraction occurs when waves pass through an aperture.

True. Diffraction occurs when waves pass through an aperture or around a barrier.

What happens to wave amplitude during diffraction through an aperture?

Wave amplitude decreases during diffraction through an aperture because the barrier on either side of the gap absorbs wave energy.

How does gap size relative to wavelength affect diffraction?

Gap size relative to wavelength affects diffraction because diffraction occurs when the gap size is similar to the wavelength. More diffraction occurs if the wavelength is larger than the gap size.

What happens when waves pass through a gap much larger than the wavelength?

When waves pass through a gap much larger than the wavelength, the majority of the wave passes straight through with little diffraction .

Define diffraction around a barrier .

Diffraction around a barrier is when waves curve around the edge of the barrier and spread out behind it.

What determines the extent of diffraction around a barrier?

The extent of diffraction around a barrier is determined by the wavelength of the waves. Longer wavelengths undergo greater diffraction.

What is the effect of a barrier larger than the wavelength on the amount of wave diffraction?

The effect of a barrier larger than the wavelength is some diffraction occurs and a shadow region forms behind the barrier where no wavefronts are present.

How does wavelength compared to barrier size affect diffraction?

Wavelength compared to barrier size affects diffraction because if the barrier is the same size as the wavelength, there is more diffraction and a smaller shadow region behind the barrier.

What is the relationship between wavelength and optimal diffraction?

Optimal diffraction occurs when the wavelength is comparable to the size of the gap or barrier.

Snell's law relates the angle of incidence to the angle of refraction at a boundary between two media.

Define the term critical angle .

The critical angle is the angle of incidence at which the angle of refraction is 90° , causing the light to travel along the boundary between media.

What does total internal reflection mean?

Total internal reflection occurs when the angle of incidence within the denser medium is greater than the critical angle.

How does the refractive index affect the speed of light in a medium?

The higher the refractive index of a material, the more optically dense it is, and the slower light will travel through it.

What is superposition?

Superposition is when two or more waves arrive at the same point and their amplitudes combine.

Define the principle of superposition .

The principle of superposition states that when two or more waves overlap at a point, the displacement at that point is the sum of the displacements of the individual waves.

True or False? Superposition only applies to transverse waves.

False. The principle of superposition applies to both transverse and longitudinal waves.

What does constructive interference mean?

Constructive interference occurs when two or more waves superimpose and have displacements in the same direction.

What is destructive interference?

Destructive interference occurs when two or more waves superimpose and have displacements in opposite directions.

How do waves interfere constructively?

Waves interfere constructively when they are in phase and their displacements add together to form a larger displacement.

What happens to waves after they undergo superposition?

After waves undergo superposition, they continue to travel as normal.

State the meaning of resultant displacement .

Resultant displacement is the vector sum of the displacements of individual waves when they overlap.

What must be constant for a clear interference pattern?

For a clear interference pattern, the waves must be of the same type , amplitude , frequency , and have a constant phase difference .

What is double-source interference?

Double-source interference involves producing a diffraction and interference pattern using either two coherent wave sources or a single wave source passing through a double slit.

State one example of a wave source that can cause double-source interference to be observed.

Double-source interference can be observed using the following wave sources: A laser beam Two speakers emitting coherent sound Microwaves diffracted through two slits

Define interference .

Interference is the effect observed due to the superposition of two or more waves.

When does constructive interference occur?

Constructive interference occurs when two waves meet in phase , resulting in the waves adding together.

When does destructive interference occur?

Destructive interference occurs when two waves meet in antiphase , resulting in the waves cancelling each other out.

True or False? Coherent waves have the same frequency and a constant phase difference.

True. Coherent waves have the same frequency and a constant phase difference.

Define path difference .

Path difference is the difference in the distance travelled by two waves from their sources to the point at which they meet.

How is interference determined from a wavefront diagram?

On a wavefront diagram, interference is determined by counting the number of wavelengths to determine if constructive or destructive interference occurs at a point.

State the features of a diffraction pattern that indicate a double-slit diffraction pattern.

The features of a diffraction pattern that indicate a double-slit diffraction pattern are: each bright fringe is identical in width and intensity the fringe spacing is equal

What is double-source interference?

Double-source interference involves producing a diffraction and interference pattern using either two coherent wave sources or a single wave source passing through a double slit.

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What is a wavefront?
A wavefront is a line joining all the points on a wave that oscillate in phase and are perpendicular to the direction of motion.
Define a ray in the context of waves.
A ray is a line showing the direction of motion and energy transfer of the wave, perpendicular to the wavefront.
True or False?
A surface wave propagates in three dimensions.
False.
A surface wave propagates in two dimensions.
What shape do wavefronts have for a surface wave?
The wavefronts for a surface wave are circular.
How are peaks and troughs represented in wavefront diagrams?
Peaks are represented with a darker line and troughs with a fainter line.
What is the distance between successive peak wavefronts called?
The distance between successive peak wavefronts is called the wavelength.
Define circular wavefronts.
Circular wavefronts are wavefronts that propagate in two dimensions, such as those on the surface of water.
What are spherical wavefronts?
Spherical wavefronts are wavefronts that propagate in three dimensions, such as those of sound or light waves.
State the relationship between wavefronts and rays.
Wavefronts are perpendicular to rays. Rays indicate the direction of motion and energy transfer of the wave.
What is the graphical representation of a transverse wave in a horizontal plane?
The graphical representation of a transverse wave in a horizontal plane shows wavefronts as parallel vertical lines.
Define reflection.
Reflection is when a wave hits a boundary between two media and bounces back to the original medium without passing through.
State the law of reflection.
The law of reflection states that the angle of incidence, $i$ , equals the angle of reflection, $r$ .
True or False?
During reflection, the frequency of the wave changes.
False.
During reflection, the frequency, wavelength, and speed of the wave do not change.
Define refraction.
Refraction is the change in direction of a wave when it passes through a boundary between mediums of different densities.
How does wave speed change when passing from a less dense to a more dense medium?
When a wave travels from a less dense medium to a more dense medium, its speed decreases.
What is the angle of incidence?
The angle of incidence is the angle between the incident ray and the normal line at the boundary between two media.
What happens to light when it travels from air to glass?
When light travels from air to glass, its speed decreases, its wavelength decreases, and it refracts towards the normal.
True or False?
Refraction occurs without transmission when a wave passes through the boundary between two media.
False.
Refraction always involves the transmission of the wave into the second medium.
Define transmission.
Transmission is when a wave passes through a substance, and refraction is a specific type of transmission involving a change in direction.
What happens to the angle of refraction when light travels from a denser to a less dense medium?
When light travels from a denser to a less dense medium, the angle of refraction is greater than the angle of incidence, causing the light to bend away from the normal.
What wave behaviour is shown in the diagram?
The wave behaviour shown in the daigram is reflection.
State why refraction does not take place when the light ray passes from air into the glass block in the diagram.
$A light ray's refraction through a rectangular glass block from air. The ray that travels perpendicular to the surfaces, is labelled as "normal."$
Refraction does not take place when the light ray passes from air into the glass block in the diagram because the ray has an angle of incidence of zero, it is incident along the normal line.
State the wave phenomena shown in the diagram.
$Wave diffraction, where incoming parallel wavefronts pass through an aperture, bending into curved wavefronts labelled "diffracted wave."$
The wave phenomenon shown in the diagram is diffraction.
$Diffraction shows straight wavefronts passing through an aperture, producing curved diffracted waves that spread outward with labelled parts.$
Define diffraction.
Diffraction is the spreading out of waves after they pass through a narrow gap or around an obstruction.
True or False?
Diffraction occurs when waves pass through an aperture.
True.
Diffraction occurs when waves pass through an aperture or around a barrier.
What happens to wave amplitude during diffraction through an aperture?
Wave amplitude decreases during diffraction through an aperture because the barrier on either side of the gap absorbs wave energy.
How does gap size relative to wavelength affect diffraction?
Gap size relative to wavelength affects diffraction because diffraction occurs when the gap size is similar to the wavelength. More diffraction occurs if the wavelength is larger than the gap size.
What happens when waves pass through a gap much larger than the wavelength?
When waves pass through a gap much larger than the wavelength, the majority of the wave passes straight through with little diffraction.
Define diffraction around a barrier.
Diffraction around a barrier is when waves curve around the edge of the barrier and spread out behind it.
What determines the extent of diffraction around a barrier?
The extent of diffraction around a barrier is determined by the wavelength of the waves. Longer wavelengths undergo greater diffraction.
What is the effect of a barrier larger than the wavelength on the amount of wave diffraction?
The effect of a barrier larger than the wavelength is some diffraction occurs and a shadow region forms behind the barrier where no wavefronts are present.
How does wavelength compared to barrier size affect diffraction?
Wavelength compared to barrier size affects diffraction because if the barrier is the same size as the wavelength, there is more diffraction and a smaller shadow region behind the barrier.
What is the relationship between wavelength and optimal diffraction?
Optimal diffraction occurs when the wavelength is comparable to the size of the gap or barrier.
What is Snell's law?
Snell's law relates the angle of incidence to the angle of refraction at a boundary between two media.
Define refractive index.
The refractive index, $n$ , of a material tells us how optically dense it is.
True or False?
The refractive index of air is 1.
True.
The refractive index of air is $n$ = 1.
What is the equation for refractive index, $n$ ?
The refractive index of a material is calculated using the equation $n = \frac{c}{v}$ .
Where:
- $n$ = absolute refractive index of the medium
- $c$ = speed of light in a vacuum, measured in metres per second (ms^-1)
- $v$ = speed of light in the medium, measured in metres per second (ms^-1)
Define the term critical angle.
The critical angle is the angle of incidence at which the angle of refraction is 90°, causing the light to travel along the boundary between media.
What does total internal reflection mean?
Total internal reflection occurs when the angle of incidence within the denser medium is greater than the critical angle.
How is Snell's law expressed in terms of sine functions?
Snell's law is expressed as: $n_{₁} \sin θ_{₁} = n_{₂} \sin θ_{₂}$
Where:
- $n_{1}$ = refractive index of medium 1
- $n_{2}$ = refractive index of medium 2
- $θ_{1}$ = angle of incidence in medium 1, measured in degrees ( $°$ )
- $θ_{2}$ = angle of refraction in medium 2, measured in degrees ( $°$ )
What are the two conditions for total internal reflection to occur?
The two conditions for total internal reflection to occur are:
- the refractive index of medium 1 < refractive index of medium 2 ( $n_{1} < n_{2}$ )
- angle of incidence > critical angle ( $θ_{i} > θ_{c}$ )
What is the equation for the critical angle, $θ_{c}$ ?
The equation for the critical angle, $θ_{c}$ , is found using the equation: $\sin θ_{c} = \frac{n_{2}}{n_{1}}$
Where:
- $n_{2}$ = refractive index of medium 2
- $n_{1}$ = refractive index of medium 1
How does the refractive index affect the speed of light in a medium?
The higher the refractive index of a material, the more optically dense it is, and the slower light will travel through it.
What is superposition?
Superposition is when two or more waves arrive at the same point and their amplitudes combine.
Define the principle of superposition.
The principle of superposition states that when two or more waves overlap at a point, the displacement at that point is the sum of the displacements of the individual waves.
True or False?
Superposition only applies to transverse waves.
False.
The principle of superposition applies to both transverse and longitudinal waves.
What does constructive interference mean?
Constructive interference occurs when two or more waves superimpose and have displacements in the same direction.
What is destructive interference?
Destructive interference occurs when two or more waves superimpose and have displacements in opposite directions.
How do waves interfere constructively?
Waves interfere constructively when they are in phase and their displacements add together to form a larger displacement.
What happens to waves after they undergo superposition?
After waves undergo superposition, they continue to travel as normal.
State the meaning of resultant displacement.
Resultant displacement is the vector sum of the displacements of individual waves when they overlap.
What must be constant for a clear interference pattern?
For a clear interference pattern, the waves must be of the same type, amplitude, frequency, and have a constant phase difference.
Name the wave phenomenon that causes the amplitude of the resultant waves in the diagram to be the sum of the amplitudes of the two individual waves.
The amplitude of the resultant waves in the diagram is the sum of the amplitude of the two individual waves because the two waves are superposed.
Determine the path difference between the waves coming from S₁ and S₂ in the diagram.
The path difference between the waves coming from S₁ and S₂ in the diagram is 2 $λ$ .
What is double-source interference?
Double-source interference involves producing a diffraction and interference pattern using either two coherent wave sources or a single wave source passing through a double slit.
State one example of a wave source that can cause double-source interference to be observed.
Double-source interference can be observed using the following wave sources:
- A laser beam
- Two speakers emitting coherent sound
- Microwaves diffracted through two slits
Define interference.
Interference is the effect observed due to the superposition of two or more waves.
When does constructive interference occur?
Constructive interference occurs when two waves meet in phase, resulting in the waves adding together.
When does destructive interference occur?
Destructive interference occurs when two waves meet in antiphase, resulting in the waves cancelling each other out.
True or False?
Coherent waves have the same frequency and a constant phase difference.
True.
Coherent waves have the same frequency and a constant phase difference.
Define path difference.
Path difference is the difference in the distance travelled by two waves from their sources to the point at which they meet.
What is the condition for constructive interference?
The condition for constructive interference is path difference = $n λ$ , where $n$ is an integer.
What is the condition for destructive interference?
The condition for destructive interference is path difference $= (n + \frac{1}{2}) λ$ , where $n$ is an integer.
How is interference determined from a wavefront diagram?
On a wavefront diagram, interference is determined by counting the number of wavelengths to determine if constructive or destructive interference occurs at a point.
State the features of a diffraction pattern that indicate a double-slit diffraction pattern.
The features of a diffraction pattern that indicate a double-slit diffraction pattern are:
- each bright fringe is identical in width and intensity
- the fringe spacing is equal
What is double-source interference?
Double-source interference involves producing a diffraction and interference pattern using either two coherent wave sources or a single wave source passing through a double slit.
True or False?
Coherent waves have the same frequency and a constant phase difference.
True.
Coherent waves have the same frequency and a constant phase difference.
How is the nature of interference determined using a wavefront diagram?
The nature of interference is determined using a wavefront diagram by counting the number of wavelengths between the two wave sources to see if it is constructive or destructive at a point.
Define monochromatic.
Monochromatic waves have the same wavelength, so for visible light, they are the same colour.
State the equipment required in Young's double slit experiment.
The equipment required in Young's double slit experiment is:
- a monochromatic light source
- a single slit
- a double slit
- a screen
State the type of diffraction observed by the screen shown in the diagram.
The type of diffraction observed on the screen shown in the diagram is double-slit diffraction.
What is a single slit diffraction pattern?
A single slit diffraction pattern is a series of light and dark fringes produced by monochromatic light passing through a single rectangular slit onto a screen.
Define central maximum in a single slit diffraction pattern.
The central maximum is the brightest and widest fringe in a single slit diffraction pattern.
True or False?
The central maximum in a single slit diffraction pattern is wider than the maxima in a double slit diffraction pattern.
True.
The central maximum in a single-slit diffraction pattern is wider than the maxima in a double-slit diffraction pattern.
How does changing the wavelength of the incident light affect the diffraction pattern in a single-slit experiment?
Increasing the wavelength of the incident light increases the angle of diffraction, causing wider fringes.
What is the relationship between slit width and the angle of diffraction in a single slit diffraction pattern?
The relationship between slit width and the angle of diffraction in a single slit diffraction pattern is inversely proportional to the slit width.
State the equation for the angle of diffraction in terms of slit width.
The equation for the angle of diffraction in terms of slit width is $θ = \frac{λ}{b}$
Where:
- $θ$ is the angle of diffraction, measured in degrees ( $°$ )
- $λ$ is the wavelength of the incident light, measured in metres (m)
- $b$ is the single slit width, measured in metres (m)
Describe the features of the dark fringes of destructive interference on the single slit diffraction pattern.
Dark fringes of destructive interference in single slit diffraction patterns:
- are narrower than the bright fringes
- are less bright than the bright fringes
- get dimmer further from the central maxima
What is the effect of narrowing the slit width in a single slit diffraction pattern?
The effect of narrowing the slit width in a single slit diffraction pattern is that it increases the angle of diffraction, creating wider fringes that are less intense.
What is the effect of increasing the distance between the slit and the screen in a single slit diffraction experiment?
Increasing the distance between the slit and the screen in a single slit diffraction experiment increases the width of the fringes.
Define the term fringe in the context of diffraction patterns.
A fringe is a bright or dark band resulting from the constructive or destructive interference of light waves.
What is a diffraction grating?
A diffraction grating is a piece of optical equipment with many parallel slits that diffract light to produce a diffraction pattern.
True or False?
Increasing the number of slits in a diffraction grating increases the intensity of the maxima.
True.
Increasing the number of slits in a diffraction grating increases the intensity of the maxima.
What does $d$ represent in the diffraction grating equation?
In the diffraction grating equation, $d$ represents the distance between the slits.
State the diffraction grating equation.
The diffraction grating equation is $n λ = d \sin θ$
Where:
- n = the order of maxima
- $λ$ = wavelength of incident light, measured in metres (m)
- $d$ = slit separation, measured in metres (m)
- $θ$ = angle of diffraction, measured in degrees ( $°$ )
Define the term angular separation in a diffraction pattern.
Angular separation is the angle between two maxima in a diffraction pattern.
Describe the diffraction pattern obtained when white light is incident in a diffraction grating.
The diffraction pattern obtained when white light is incident in a diffraction grating is different wavelengths of light separated into spectra.
How does decreasing the slit spacing, $d$ , affect the diffraction pattern produced on a screen?
Decreasing the slit spacing increases the angle of diffraction, creating wider fringes.
Which wavelength appears closest to the central maximum in a diffraction pattern of white light?
The shortest wavelength, violet/blue, appears closest to the central maximum in a diffraction pattern of white light.
What is the definition of the order of maxima?
The order of maxima is the number representing the position of a bright fringe from the central maximum.
State the trigonometric relationship between the wavelength, $λ$ , slit separation, $θ$ , and angle of diffraction, $θ$ , as shown in the diagram.
$Light waves diffract through many slits. Red arrows indicate incident light, blue dashed line shows normal line, and angles of diffraction, θ, are marked.$
The trigonometric relationship between the wavelength, $λ$ , slit separation, $θ$ , and angle of diffraction, $θ$ , as shown in the diagram is: $\sin θ = \frac{λ}{d}$
$Diagram illustrating light diffraction through a single slit. It shows angles theta, slit width d, wavelength lambda, and the formula sin(theta) = lambda/d.$