5A2 Wave Phenomena Flashcards
Explore wave phenomena, processes, and effects such as reflection, refraction, harmonics, polarization, and more.
Define:
Wave reflection
The change in direction of propagation of a wave that strikes a boundary between two materials.
Wave reflection occurs when a wave meets a barrier and bounces off in another direction.
Define:
Angle of incidence
The angle between the incident ray and the normal line at the point of contact.
The normal is a perpendicular line to the surface at the point where the wave strikes the surface.
What does the law of reflection state?
The angle of incidence is equal to the angle of reflection.
Mathematically, it can be written as θi = θr, where θi is the angle of incidence and θr is the angle of reflection.
Fill in the blank:
_____ ______ is the bending of waves as it passes from one medium to another.
Wave refraction
It occurs when a wave hits the surface of a different medium.
What happens to a light ray when it passes from air to water?
The light ray slows down and bends toward the normal line.
The normal is the line perpendicular to the air-water interface.
What is the index of refraction?
It quantifies the ratio between the speed of light in a vacuum and the speed of light in the material.
It is expressed as n = c/v and is dimensionless.
True or false:
Snell’s Law relate the incident angle and the refracted angle.
True
It is based on the indices of refraction of both materials.
What is the equation for Snell’s Law?
n1sin(θ1) = n2sin(θ2)
Here, n1 and n2 are the indices of refraction for the two materials, and θ1 and θ2 are the incident and refracted angles, respectively.
What happens to light when it passes from a material with a higher index of refraction to a lower index?
Light bends away from the normal line.
If the incident angle is large enough, total internal reflection occurs.
When does total internal reflection occur?
It occurs when all light is reflected back into a material instead of passing into another material.
This phenomenon is utilized in fiber optic cables.
True or false:
The critical angle is the angle of incidence at which total internal reflection occurs.
True
It can be calculated using the indices of refraction of the two materials.
Define:
Diffraction
Bending of light waves around obstacles or the spreading of light waves as they pass through small openings.
The extent of diffraction depends on the size of the obstacle or slit compared to the wavelength of the light.
True or false:
Diffraction only occurs when light passes through very large openings.
False
Diffraction occurs when light passes through openings or around obstacles that are comparable in size to the wavelength of the light. Diffraction is most noticeable when the size of the slit or obstacle is on the order of the wavelength of the light.
True or false:
Interference patterns can only occur with light waves.
False
All waves—sound, water, or light—can show interference through superposition.
What is the condition for destructive interference?
When waves are out of phase with a path difference of (2n+1)λ/2,
It reduces wave amplitude, forming dark fringes in patterns.
How does the uncertainty principle affect the double-slit experiment?
It limits observing both particle and wave behavior at the same time.
## Footnote
The principle indicates that measuring one property disturbs the other.
Fill in the blank:
The double-slit experiment shows that light can behave like a _____.
wave
This behavior is evidenced by the interference patterns observed in the experiment.
True or false:
In Young’s double-slit experiment, the bright fringes occur at angles where the path difference is an integer multiple of the wavelength.
True
Bright fringes are produced when there is constructive interference.
The condition for constructive interference is d * sin(θ) = m * λ, where d is the slit separation, θ is the angle of the bright fringe, m is an integer (order of the fringe), and λ is the wavelength of light.
What kind of light source is used in Young’s double-slit experiment?
A monochromatic source of light.
This ensures a single wavelength is used for the experiment.
Define:
polarization
in the context of light
Filtering out chaotic light-wave oscillations to achieve a clearer experience of light.
Polarization allows light to oscillate in a specific direction, making it more organized.
How does polarized light differ from unpolarized light?
Polarized light vibrates in one direction; unpolarized light vibrates in many.
Sunlight is unpolarized; polarizing filters produce polarized light.
What is a polarizer?
A device that allows light oscillating in a particular direction to pass through while blocking other directions.
Think of it like a card with slits that only permits certain light waves.
List some uses of polarizers.
- Polarizing sunglasses
- Polarizing filters for cameras
- LCD screens
- Radio transmissions
These applications utilize the ability of polarizers to manage light in various contexts.
What does Malus’s Law describe?
The relationship between the intensity of light that passes through a polarizer and the angle of oscillation.
It quantifies how much light is lost when passing through a polarizer.
Fill in the blank:
Malus’s Law indicates that the intensity of light that passes through a polarizer is equal to the original intensity multiplied by ______.
cos²(θ)
The squared term is crucial in the calculation.
True or false:
The reflected light becomes polarized.
True
This polarization can be managed by polarizers to reduce glare.
True or false:
Brewster’s Law allows us to find the angle at which the reflected light becomes completely polarized.
True
At Brewster’s angle, the reflected light is completely polarized, and this principle is used in various optical applications.
What is the formula for Brewster’s angle?
θB = tan⁻¹(n2/n1)
θB is Brewster’s angle, and n1 and n2 are the refractive indices of the two media.
How do polarizing filters work in photography?
They allow only certain polarized light rays to pass through, reducing reflections and enhancing contrast.
They are particularly effective for darkening skies and eliminating reflections from glass or water.
Define:
Scattering of light
The diffusive effect of particles causing light waves to deviate from their straight paths.
It involves absorption and re-emission of light in various directions.
What are the two main types of scattering of light?
- Elastic scattering
- Inelastic scattering
Elastic scattering has no change in wavelength, while inelastic scattering involves a change in the inner energy of molecules.
What is an example of inelastic scattering?
Raman scattering
It involves the interaction of light with molecules resulting in a loss or gain of energy.
What is Rayleigh scattering?
It occurs when light interacts with particles that are much smaller than the wavelength of the light in question.
This causes shorter wavelengths to scatter more than longer wavelengths.
True or false:
Mie scattering explain blue color of the sky.
False
This phonomenon is explained by Rayleigh scattering.
What is the Tyndall effect?
The scattering of light by particles in a colloid or fine suspension, making the light beam visible.
This effect is often seen when sunlight passes through fog or dusty air.
Fill in the blank:
______ ___________ occurs when the scattering particles are comparable to or larger than the wavelength of the incident light, resulting in less wavelength-dependent scattering.
Mie scattering
It explains the white appearance of clouds, as it affects all visible wavelengths equally.
What happens to light during a reddish sunset?
Longer wavelengths reach the eyes as shorter wavelengths are scattered away.
The sun’s rays travel a longer distance through the atmosphere at sunset.
What is wave absorption?
The transfer of energy from a wave to a medium, such as solid, liquid, or gas.
Wave absorption occurs when waves like sound or light hit a medium and transfer energy.
What happens to the energy of a wave during absorption?
The energy is converted into heat as the atoms and molecules within the object vibrate.
Sometimes the wave is only partially absorbed, leading to lower energy levels being transferred.
Why do black objects appear black?
They absorb all colors of visible light, holding a great amount of energy and transferring it to heat.
This is why many homes have black roofs, which help keep them cool by trapping heat.
Fill in the blank:
Soft materials absorb sound waves to decrease noise levels, changing the _______ and lowering the volume.
frequency
Foam padding is an example of a material used for soundproofing.
What does wave dispersion describe?
The separation of light of different frequencies by different amounts.
This is often demonstrated using a prism to separate white light into colors.
How do rainbows form?
Through reflection, refraction, and dispersion of light.
Dispersion separates white light into its components based on varying wavelengths.
What is the difference between dispersion and diffusion?
- Dispersion is predictable based on frequency.
- Diffusion is random.
Diffusion occurs when light is scattered off a rough surface or passes through an irregular medium.
What happens when light is transmitted through a material?
Light passes through the medium without being absorbed or reflected, although it may be refracted depending on the material’s properties.
The amount of transmission depends on the material’s transparency and the wavelength of the light.
True or false:
A material’s transparency determines how much light can pass through it.
True
Transparent materials allow most light to pass through, while opaque materials block it completely.
What is the difference between wave absorption, wave transmission, and wave reflection?
Absorption involves energy being taken in, transmission involves passing through without energy transfer, and reflection involves bouncing back.
Examples include light waves hitting mirrors (reflection) and light passing through windows (transmission).
Define:
Natural frequency
Frequency at which a system tends to oscillate when disturbed from its rest position without external forces acting on it.
Every object or system has its own characteristic natural frequency.
What is resonance in a physical system?
It occurs when an object or system vibrates at its natural frequency due to an external force, causing an increase in amplitude.
This phenomenon can be observed in musical instruments, bridges, or even in the design of buildings.
Fill in the blank:
The frequency of the second harmonic is ______ the fundamental frequency.
twice
Each successive harmonic is an integer multiple of the fundamental frequency.
What is the relationship between resonance and harmonics?
Resonance happens when an external force matches a harmonic frequency, amplifying the vibration.
Higher harmonics can also resonate if their frequencies match the driving force’s frequency.
True or false:
When the source of the wave is moving towards the observer, the frequency of the wave increases.
True
This is explained by the Doppler effect. When the source approaches the observer, the waves are compressed, resulting in a higher observed frequency (blue shift for light waves).
How does sound change when an observer moves toward a stationary source?
The sound’s frequency and pitch appear higher.
More wavefronts reach the observer per second, increasing perceived frequency.
True or false:
The Doppler effect can be observed with both sound and light waves.
True
For light, the effect causes a shift toward the blue end of the spectrum when moving toward the observer (blue shift) and toward the red end when moving away (red shift).
What is the general formula for the Doppler effect?
f’=f[(v±v0)/(v±vs)]
Where f’ is the observed frequency, f is the emitted frequency, v is the wave speed, v0 is the observer’s speed, and vs is the source’s speed.
How is the Doppler effect used in astronomy?
It helps astronomers determine the motion of stars and galaxies by analyzing the red and blue shifts in light from these objects.
The red shift indicates objects are moving away, while blue shift indicates they are moving toward Earth.
