5A1 Types and Characteristics of Waves Flashcards
Define the types and characteristics of waves, including the relationships between their characteristics.
Define:
Wave
Propagation of a repeating, periodic disturbance from place to place.
This disturbance transfers energy through matter or space without the movement of matter itself.
True or false:
Waves can only transfer energy through solids.
False
Waves can travel through solids, liquids, and gases, depending on the type of wave.
How is a wave typically represented graphically?
As a sine or cosine curve, where the x-axis represents time or distance, and the y-axis represents displacement or amplitude.
The peaks of the wave represent the maximum displacement (crest), while the troughs represent the minimum displacement (trough).
Fill in the blank:
A(n) _______ is an instrument commonly used to visualize and measure waveforms, including amplitude, frequency, and phase.
oscilloscope
An oscilloscope displays waveforms on a screen, allowing detailed analysis of wave properties in real-time.
Why are waves important in physics?
They explain how energy, sound, light, and radiation are transferred.
They play a key role in communication, medicine, and many natural phenomena.
Define:
Amplitude
Maximum displacement of particles from their equilibrium position in a wave.
It determines the wave’s energy in mechanical waves.
Explain the relationship between frequency and period in a wave.
The frequency is the reciprocal of the period: f=1/T.
Frequency is measured in Hertz (Hz), while the period is measured in seconds (s).
True or false:
Higher frequency waves have longer wavelengths.
False
Wavelength decreases as frequency increases.
Fill in the blanks:
The speed of a wave (v) is equal to the product of its ______ and ______.
frequency; wavelength
The formula is v=f⋅λ.
What is the unit of measurement for frequency?
Hertz (Hz)
Frequency is measured in hertz, which indicates the number of cycles per second.
What happens to the energy of a wave if the amplitude doubles?
The energy becomes four times greater.
Wave energy is proportional to the square of the amplitude.
What are the formulas for the kinetic and potential energy of a wave?
- Kinetic Energy: KE=1/2 ρv²A² sin²(kx−ωt)
- Potential Energy: PE=1/2 ρv²A² cos²(kx−ωt)
In the equations, ρ = medium density, v = wave speed, A = amplitude, k = wave number, ω = angular frequency.
How does light’s speed differ between air and water?
Light travels slower in water than in air.
This change in speed causes refraction.
True or false:
The wavelength of a wave is the distance between consecutive crests or troughs.
True
This applies to transverse waves.
What is the SI unit of wavelength?
Meter (m)
Wavelength represents the distance between two consecutive points in phase, such as two crests or two troughs.
What is the formula for the wave number?
k= 2π/λ
λ is the wavelength. Wave number (k) indicates how many wave cycles fit into a unit length.
Why does sound travel faster in steel than in air?
The particles in steel are more tightly packed, allowing faster energy transfer.
Mechanical waves move faster in solids due to stronger particle interactions.
Define:
Transverse wave
A wave in which the particles of the medium move perpendicular to the direction of wave propagation.
Light waves are an example of transverse waves.
Fill in the blank:
In a ______ wave, the medium’s particles oscillate parallel to the wave’s direction.
longitudinal
Examples include sound waves.
True or false:
Sound waves are transverse waves.
False
Sound waves are longitudinal waves. Longitudinal waves have particle motion parallel to the wave direction.
Why are water waves classified as both transverse and longitudinal?
Water particles move in circular paths, combining perpendicular and parallel motions to the wave propagation.
This is called an orbital wave motion.
What type of wave is created by a vibrating string?
Transverse wave
The vibration creates perpendicular disturbances along the string.
Define:
Compression in a longitudinal wave
A region where particles are close together in a longitudinal wave.
Opposite to rarefaction.
True or false:
Earthquake S-waves are transverse.
True
They move the ground up and down or side to side.
What is the difference between P-waves and S-waves?
- P-waves: Longitudinal, fastest, travel through solid and liquid.
- S-waves: Transverse, second fastest, only travel through solids.
Both are types of seismic waves caused by earthquakes.
What are Rayleigh waves?
Surface waves that travel along the surface of solids, causing both vertical and horizontal ground motion.
They are a type of seismic wave. Rayleigh waves are slower than body waves (P-waves and S-waves) and are responsible for most of the shaking felt during an earthquake.
Fill in the blank:
A wave that requires a medium to travel through is called a _______ wave.
mechanical
Examples include sound waves and water waves.
True or false:
Electromagnetic waves require a medium to travel.
False
Electromagnetic waves can travel through the vacuum of space.
Explain why mechanical waves cannot travel through a vacuum.
They require interactions between particles in a medium to transfer energy, which is absent in a vacuum.
Sound cannot travel in space for this reason.
Provide an example of an electromagnetic wave and describe its application.
X-rays, used in medical imaging.
They can penetrate soft tissue but are absorbed by bones.
True or false:
Mechanical waves can be either transverse or longitudinal.
True
Water waves are transverse, while sound waves are longitudinal.
Explain why radio signals can travel from satellites to Earth.
They waves are electromagnetic and can travel through the vacuum of space.
They do not need a medium for transmission.
Define:
Electromagnetic spectrum
Range of all types of electromagnetic radiation, classified by their wavelengths or frequencies.
It includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
What are the main components of an electromagnetic wave?
- An electric field
- A magnetic field
They oscillate perpendicular to each other and to the direction of wave propagation.
What is the speed of electromagnetic waves in a vacuum?
The speed of light (approximately 3.00 × 10⁸ m/s).
This speed is constant for all types of electromagnetic radiation in a vacuum, regardless of frequency or wavelength.
How is the energy of an electromagnetic wave related to its frequency?
It is directly proportional to its frequency.
It is given by the equation E=h×f, where E is the energy, h is Planck’s constant, and f is the frequency.
What does the principle of superposition of waves state?
When two or more waves overlap, their displacements combine to form a resultant wave.
This can cause constructive or destructive interference.
What is the phase of a wave?
Position of a point within a wave cycle, typically measured in degrees or radians.
Phase differences between waves determine whether they interfere constructively or destructively.
When are two waves considered in phase?
When their crests and troughs occur at the same time and position.
When waves are in phase, their amplitudes combine to form a wave with greater overall amplitude.
True or false:
When two waves are in phase, destructive interference occurs.
False
Waves in phase produce constructive interference.
Fill in the blank:
When two waves are ______, their peaks and troughs align perfectly.
in phase
This results in constructive interference.
What is constructive interference?
It occurs when the compression of one sound wave coincides with the compression of another sound wave.
Similar results occur with light waves when peaks coincide.
What is an example of superposition in day-to-day life?
Noise-canceling headphones use destructive interference to reduce ambient sound.
Microphones capture sound waves and generate opposite waves.
Define:
Interference patterns
Result of the superposition of two or more waves, creating regions of constructive interference (increased amplitude) and destructive interference (reduced amplitude).
Interference patterns provide evidence of the wave nature of phenomena, such as light in the famous double-slit experiment.
True or false:
Interference patterns are observed in both sound and light waves.
True
Light interference creates patterns of bright and dark fringes.
Define:
Wave intensity
The power carried by a wave per unit area, measured perpendicular to its direction.
It is measured in watts per square meter (W/m²).
True or false:
Wave intensity increases as the distance from the source increases.
False
Intensity decreases as the distance from the source increases due to energy dispersion.
Fill in the blank:
Intensity is proportional to the square of the _______ of a wave.
amplitude
Doubling the amplitude quadruples the intensity.
What is the formula for wave intensity?
I=P/A
Where I is intensity, P is power, and A is the area.
How do you calculate the power of a wave?
P=1/2 ρvω²A²
P∝A²; doubling the amplitude increases the power fourfold.
How does intensity relate to sound perception?
Higher intensity results in louder sounds.
The human ear perceives sound intensity logarithmically.
What is a resultant wave?
The result of combining two or more waves or superposing waves.
This concept is central to understanding wave behavior.
What is the relationship between wave intensity and energy transfer?
Higher intensity indicates greater energy transfer per unit area.
This applies to both mechanical and electromagnetic waves.
Define:
Spherical wave
Wave that propagates outward in all directions from a point source, forming spherical wavefronts.
Sound waves from a small speaker are an example.
True or false:
Plane waves maintain parallel wavefronts as they propagate.
True
Light waves from a distant laser can approximate plane waves.
Fill in the blank:
In spherical waves, wave intensity decreases according to the ______ _____ law.
inverse square
Intensity is inversely proportional to the square of the distance from the source.
What happens to a spherical wave as the distance from the source increases?
The wavefronts become less curved and can approximate plane waves at great distances.
This transition is useful in optics.
How are plane waves useful in physics experiments?
They simplify wave analysis by assuming constant phase and amplitude across wavefronts.
This assumption is valid in controlled conditions.
Provide a real-world example of a spherical wave.
Sound waves from a fire alarm propagate as spherical waves.
The sound spreads in all directions.
Define:
Standing wave
Waves that oscillate in time but do not move in space.
It is formed when two waves of the same frequency and amplitude traveling in opposite directions interfere.
Fill in the blank:
In a standing wave, ______ are points where there is no displacement.
nodes
These points remain stationary.
True or false:
Nodes in a standing wave have the highest amplitude.
False
Antinodes have the highest amplitude.
What is the relationship between the wavelength and the length of a string fixed at both ends?
The wavelength is twice the length of the string for the fundamental frequency.
Higher harmonics have shorter wavelengths.
How does the formation of standing waves affect resonance in cavities?
Standing waves enhance resonance by reinforcing specific frequencies.
This is exploited in lasers and musical instruments.
What is the formula for the frequency of a standing wave?
f_n = nv/(2L)
L is the length of the string, n is the number of antinodes, and v is the velocity of the waves.
What are harmonics in standing waves?
A set frequency corresponding to a specific number of antinodes.
Standing waves can only have a fixed value of frequency.
What is the fundamental frequency of a standing wave?
The lowest frequency at which a standing wave forms; also known as the first harmonic.
The wavelength of the fundamental is λ1=2L, where L is the length of the medium.
What is the formula for the wavelength of the n-th harmonic in a standing wave?
λn= 2L/n
n is the harmonic number, and L is the length of the vibrating medium.
How are the frequencies of harmonics related to the fundamental frequency?
fn =n⋅f1
Higher harmonic frequencies are integer multiples of the fundamental frequency f1.
Provide an example of a practical application of standing waves.
Microwave ovens use standing waves to heat food.
The antinodes deliver maximum energy for heating.
