Waves Flashcards
Wave
A disturbance that carries energy from one place to another.
Transverse Waves
Waves in which the direction of vibration is perpendicular to the propogation to the wave.
Longitudinal Waves
Waves in which the direction of vibration is parallel to the propogation to the wave.
Mechanical Waves
The vibration of particles.
Electromagnetic Waves
(EM) waves are the disturbance/vibration of electric and magnetic (electromagnetic) fields.
Periodic Travelling Waves
Regularly repeating cycle that appears to move in the direction of propogation to the wave.
Crest
The highest point of a transverse wave.
Trough
The lowest point of a transverse wave.
Oscillation
(or cycle), is one complete vibration of the source.
Wavelength
(λ), is the disturbance from a point on a wave to the corresponding point on an adjacent wave.
(crest to crest, etc.)
Frequency
(f), is the number of waves passing a point per second.
Amplitude
(A), is the maximum distance from a wave from its undisturbed position.
Reflection
When a wave bounces off an object in its path.
Refraction
The changing of direction of wave when it goes from one medium to another.
Diffraction
The spreading out of a wave into the space beyond a barrier.
Interference
The addition of two or more waves, forming a single resulatant wave.
Constructive Interference
When two or more waves combine, resulting in a single wave of greater amplitude than the source waves.
Coherent Wave Sources
When sources produce waves of the same frequency that are either in phase or a constant phase difference apart.
Waves In Phase
When the crests from one source meet crests from another.
Destructive Interference
When two or more waves combine, resulting in a wave of smaller amplitude than the source waves.
Waves Out Of Phase
When the crests from one source meet the troughs from another.
Interference Pattern
The pattern formed when waves from two (or more) coherent sources combine; it contains a repeating pattern of constructive and destructive interference.
Polarisation
When the direction of vibration of a wave is restricted to one plane.
Doppler Effect
The apparent change in frequency of waves due to the relative motion between a wave source and observer.
Red Shift
Doppler Effect of light observed when an star moves away from us (earth), making its light appear more red as its apparent wavelength is lower than its true wavelegth.
Sound
Form of energy that travels by longitudinal mechanical waves.
Natural Frequency
The frequency at which a body oscillates at when vobrating freely.
Resonance
The rapid amplimication of oscillation when a periodic force is applied at the same frequency as the natural frequency of the body.
Stationary Wave
A wave that remains in a constant position; it is made up of a series of nodes and antinodes.
Nodes
Points where there is no vibration.
Antinodes
Points where there is maximum vibration.
Fundamental Frequency
Lowest natural frequency of a vibrating object.
Harmonics
Multiples of the fundamental frequency.
Sound Intensity
(I), the rate at which sound energy passes through unit area at right angles to the direction of the propogation of the wave.
Threshold of Hearing
(I₀), the smallest sound intensity detectable by the average human ear at a frequency of 1 kHz
(Its value is 1 x 10^-12 W m ^-2)
Sound Intensity Level
(I.L.), a scale that compares a particular sound intensity to the treshold of hearing.
(Doubling the sound intensity LEVEL increases the sound intensity by 3dB)
(I.L. = 10log(I/I₀)
Decibel Adapted Scale
dB(A), a sound intensity level scale that has been adapted for the ear’s frequency response.
Light
Form of energy that travels by electromagnetic Waves.
Reflection
The way in which light “bounces” off surfaces.
Diffuse Reflection
The way in which lightis reflected off an object that one would not normally regard as reflective.
Regular Reflection
The way in which light reflects off smooth surfaces like mirrors.
Laws of Reflection
Law 1: The incident ray, normal and the reflected ray are all in the same plane.
Law 2: The angle of reflection (r) is equal to the angle of incidence (i).
Real Image
The actual intersection of light rays.
Virtual Images
The apparent intersection of light rays.
Refraction
The way in which light “bends” when it passes from one medium to another.
Refractive Index of a Medium
(n), is the ration of Sin(i) to Sin(r) when the light travels from a vacuum to that medium.
Total Internal Reflection.
The optical phenomenon where light is reflected back from a boundary between two media.
It occurs when the light travelling towards the rarer medium from the denser one, striking the boundary with an angle of incidence greater than the critical angle for those two media.
Critical Angle
The angle of incidence in the denser medium which causes an angle of refration of 90°
Power of a Lens
The inverse of the focal length
Compound lenses
combinations of two or more lenses in contact with each other.
Accomodation
The process of adjusting the focal length of the lens to focus distant or near objects clearly onto the retina.
Short-Sightedness
(Myopia), when distant objects cannot be seen clearly.
Long-Sightedness
(Hyperopia), when near objects cannot be seen clearly.
Light
Energy that travels by electromagnetic waves.
Spectrum
Range of wavelengths present in the electromagnetic radiation.
Dispersion
The spreading out of the different wavelengths of light.
