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Fundamental Wave Properties to Know for AP Physics 2 (2025)
Waves
are disturbances that move energy across space or a medium without moving matter.
They can be mechanical (like sound) or electromagnetic (like light), and they are defined by characteristics like wavelength, frequency, amplitude, and speed.
They exhibit behaviors including reflection, refraction, diffraction, and interference.
Types of Waves
Mechanical Waves
Require a medium for propagation, such as a solid, liquid, or gas.
These waves cannot travel in a vacuum, but they can move energy across a material by making particles vibrate or oscillate.
The density, elasticity, and other characteristics of the medium affect how fast mechanical waves travel.
Examples: Sound waves, water waves, and seismic waves.
There are two main types of mechanical waves:
Transverse Waves
The direction of wave propagation is perpendicular to the movement of the medium's particles.
Examples: Waves on a string and light waves
Longitudinal Waves
The direction of wave propagation is parallel to the movement of the medium's particles.
Examples: compression waves in a spring and sound waves.
Electromagnetic Waves
may move at the speed of light through a vacuum without the need for a medium.
They result from the movement of charged particles, which create varying magnetic and electric fields that travel through space.
These waves come in a variety of forms, including radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays, depending on their wavelength and frequency.
Examples: X-rays, Light waves, and radio waves.
Matter waves
are connected to matter particles and explained by quantum physics, which shows that particles have both particle and wave-like properties.
Instead than describing a particle's precise location, these waves—often called de Broglie waves—describe the probability distribution of its position and momentum.
Louis de Broglie first presented the idea of matter waves, arguing that all matter, not only light, may behave like waves.
Example: Electron waves
Characteristics of Waves
Wavelength (λ):
the distance between two succeeding points in phase, such as trough to trough or crest to crest.
The wavelength is a key characteristic of both mechanical and electromagnetic waves, and it is inversely related to the wave's frequency.
measured in meters (m).
Frequency (f):
the number of waves pass a specific location in a second.
It is a fundamental property of all waves and determines how often the wave oscillates.
measured in hertz (Hz)
Time (T):
The time it takes for a wave to pass a point in one complete cycle.
It is the inverse of frequency, meaning that the period and frequency are related by the formula:
T=1/f
Where:
T is the period of the wave
f is the frequency of the wave
measured in seconds (s)
Amplitude (A):
the maximum displacement from the state of equilibrium (rest).
It is a measure of the wave's intensity or energy.
Depending on the type of wave, measured in meters (m) or other relevant units.
Wave Speed (v):
The speed at which the wave moves through the medium, indicating how fast the energy is transmitted by the wave.
The wave speed is related to both the frequency and wavelength of the wave by the equation:
v=f⋅λ
Where:
v is the wave speed
f is the frequency
λ is the wavelength.
measured in m/s (meters per second).
Wave Behavior
Reflection
happens when a wave strikes a surface or barrier and returns to the same medium instead of being absorbed or passed through.
All waves, including sound, light, and water waves, exhibit this behavior. The angle at which a wave strikes a surface (the angle of incidence) and the angle at which it reflects off of it (the angle of reflection) are always equal.
This is the fundamental idea behind reflection. his relationship is described as:
θi=θr
Where:
θi is the angle of incidence, the angle between the incoming wave and the normal.
θr is the angle of reflection, the angle between the reflected wave and the normal.
Refraction
is a wave's direction change brought on by a change in speed as it moves through various mediums. A wave bends as it enters a new medium at an angle because its wavelength and speed change.
The angle of incidence and the variation in wave speed between the two media determine how much bending occurs.
The connection between the angles of incidence and refraction is described by Snell's Law:
n₁sinθ₁=n₂sinθ₂
Where:
n₁ and n₂ are the refractive indices of the two media
θ₁ is the angle of incidence
Θ₂ is the angle of refraction
Diffraction
is the way waves bend in order to pass through gaps and around obstacles. When waves hit a slit or obstacle, they disperse, forming a pattern that varies according to the opening of the impediment's size in relation to the wave's wavelength.
When the wave's wavelength is similar to the size of the obstacle or opening, diffraction is more apparent.
For example:
Even if the direct path is blocked, sound waves can still be heard clearly on the other side when they pass through a small door or around a corner.
Similar to sound waves, light waves can also diffract around the edges of objects, however this impact is often minimal for visible light due to its much smaller wavelength.
Interference
is used to describe how two or more waves can superimpose to create a new wave pattern. A resultant wave is created when two waves collide and combine their amplitudes.
This can result in either destructive or constructive interference, where the waves cancel each other out or enhance one another.
Constructive Interference
occurs when the crests and troughs of two waves line up, indicating that they are in phase. This causes the amplitude to grow, strengthening the wave's intensity.
A louder sound is produced, for instance, when two sound waves with the same frequency and amplitude collide in phase.
Destructive Interference
occurs when the crest of one wave coincides with the trough of another, indicating that two waves are out of phase. This causes the amplitude to diminish, and if the waves are fully out of phase, they can cancel each other out and produce no net wave.
In terms of sound, this can result in a reduced volume or, in the event of total cancellation, silence.
Fundamental Wave Properties to Know for AP Physics 2 (2025)
Waves
are disturbances that move energy across space or a medium without moving matter.
They can be mechanical (like sound) or electromagnetic (like light), and they are defined by characteristics like wavelength, frequency, amplitude, and speed.
They exhibit behaviors including reflection, refraction, diffraction, and interference.
Types of Waves
Mechanical Waves
Require a medium for propagation, such as a solid, liquid, or gas.
These waves cannot travel in a vacuum, but they can move energy across a material by making particles vibrate or oscillate.
The density, elasticity, and other characteristics of the medium affect how fast mechanical waves travel.
Examples: Sound waves, water waves, and seismic waves.
There are two main types of mechanical waves:
Transverse Waves
The direction of wave propagation is perpendicular to the movement of the medium's particles.
Examples: Waves on a string and light waves
Longitudinal Waves
The direction of wave propagation is parallel to the movement of the medium's particles.
Examples: compression waves in a spring and sound waves.
Electromagnetic Waves
may move at the speed of light through a vacuum without the need for a medium.
They result from the movement of charged particles, which create varying magnetic and electric fields that travel through space.
These waves come in a variety of forms, including radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays, depending on their wavelength and frequency.
Examples: X-rays, Light waves, and radio waves.
Matter waves
are connected to matter particles and explained by quantum physics, which shows that particles have both particle and wave-like properties.
Instead than describing a particle's precise location, these waves—often called de Broglie waves—describe the probability distribution of its position and momentum.
Louis de Broglie first presented the idea of matter waves, arguing that all matter, not only light, may behave like waves.
Example: Electron waves
Characteristics of Waves
Wavelength (λ):
the distance between two succeeding points in phase, such as trough to trough or crest to crest.
The wavelength is a key characteristic of both mechanical and electromagnetic waves, and it is inversely related to the wave's frequency.
measured in meters (m).
Frequency (f):
the number of waves pass a specific location in a second.
It is a fundamental property of all waves and determines how often the wave oscillates.
measured in hertz (Hz)
Time (T):
The time it takes for a wave to pass a point in one complete cycle.
It is the inverse of frequency, meaning that the period and frequency are related by the formula:
T=1/f
Where:
T is the period of the wave
f is the frequency of the wave
measured in seconds (s)
Amplitude (A):
the maximum displacement from the state of equilibrium (rest).
It is a measure of the wave's intensity or energy.
Depending on the type of wave, measured in meters (m) or other relevant units.
Wave Speed (v):
The speed at which the wave moves through the medium, indicating how fast the energy is transmitted by the wave.
The wave speed is related to both the frequency and wavelength of the wave by the equation:
v=f⋅λ
Where:
v is the wave speed
f is the frequency
λ is the wavelength.
measured in m/s (meters per second).
Wave Behavior
Reflection
happens when a wave strikes a surface or barrier and returns to the same medium instead of being absorbed or passed through.
All waves, including sound, light, and water waves, exhibit this behavior. The angle at which a wave strikes a surface (the angle of incidence) and the angle at which it reflects off of it (the angle of reflection) are always equal.
This is the fundamental idea behind reflection. his relationship is described as:
θi=θr
Where:
θi is the angle of incidence, the angle between the incoming wave and the normal.
θr is the angle of reflection, the angle between the reflected wave and the normal.
Refraction
is a wave's direction change brought on by a change in speed as it moves through various mediums. A wave bends as it enters a new medium at an angle because its wavelength and speed change.
The angle of incidence and the variation in wave speed between the two media determine how much bending occurs.
The connection between the angles of incidence and refraction is described by Snell's Law:
n₁sinθ₁=n₂sinθ₂
Where:
n₁ and n₂ are the refractive indices of the two media
θ₁ is the angle of incidence
Θ₂ is the angle of refraction
Diffraction
is the way waves bend in order to pass through gaps and around obstacles. When waves hit a slit or obstacle, they disperse, forming a pattern that varies according to the opening of the impediment's size in relation to the wave's wavelength.
When the wave's wavelength is similar to the size of the obstacle or opening, diffraction is more apparent.
For example:
Even if the direct path is blocked, sound waves can still be heard clearly on the other side when they pass through a small door or around a corner.
Similar to sound waves, light waves can also diffract around the edges of objects, however this impact is often minimal for visible light due to its much smaller wavelength.
Interference
is used to describe how two or more waves can superimpose to create a new wave pattern. A resultant wave is created when two waves collide and combine their amplitudes.
This can result in either destructive or constructive interference, where the waves cancel each other out or enhance one another.
Constructive Interference
occurs when the crests and troughs of two waves line up, indicating that they are in phase. This causes the amplitude to grow, strengthening the wave's intensity.
A louder sound is produced, for instance, when two sound waves with the same frequency and amplitude collide in phase.
Destructive Interference
occurs when the crest of one wave coincides with the trough of another, indicating that two waves are out of phase. This causes the amplitude to diminish, and if the waves are fully out of phase, they can cancel each other out and produce no net wave.
In terms of sound, this can result in a reduced volume or, in the event of total cancellation, silence.
