Wave properties, interference, diffraction, standing waves, sound, EM spectrum, Doppler ยท 31 terms
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A disturbance that transfers energy through a medium without causing a net displacement of the medium.
Ocean waves pass through water but a floating cork just bobs up and down โ it doesn't travel with the wave.
The material through which a wave travels (required for mechanical waves, not electromagnetic).
Waves that require a physical medium to travel through.
Sound cannot travel through space โ it needs air, water or another medium.
Examples: sound, water waves, seismic waves.
Waves that do not require a medium โ they can travel through a vacuum. They travel at c = 3ร10โธ m/s.
Light, radio, X-rays all travel through the vacuum of space โ no medium needed.
All EM waves have the same speed in a vacuum.
A wave that propagates through a medium, transferring energy from source to receiver.
The ripples from a stone dropped in water travel outward โ energy moves, water mostly stays.
A wave where the vibrations are perpendicular to the direction of propagation.
Shake a rope up and down while it stretches horizontally โ the wave is transverse.
Examples: light, all EM waves, water waves.
A wave where the vibrations are parallel to the direction of propagation.
Sound is longitudinal โ air molecules compress and expand along the same direction the sound travels.
Examples: sound waves, P-waves (seismic).
The number of complete waves (oscillations) passing a point per second.
Higher frequency sound = higher pitch.
f = 1/T = v/ฮป
The distance between two successive points in phase on a wave (e.g. crest to crest, trough to trough).
The maximum displacement of a particle from its rest (mean) position.
Louder sound = larger amplitude. Brighter light = larger amplitude.
The time for one complete oscillation of the wave.
T = 1/f
The speed at which the wave pattern (energy) propagates through the medium.
v = fฮป. Must know this formula.
Sources that are in phase and have the same frequency.
Laser light is coherent โ all waves in step. This allows clear interference patterns.
The superposition of two or more waves in the same medium, forming a resultant wave whose amplitude is the algebraic sum of the individual amplitudes.
Two speakers producing the same frequency: loud spots (constructive) and quiet spots (destructive) around the room.
Requires coherent sources for a stable pattern.
When two waves combine to produce a resultant wave with greater amplitude than either individual wave.
Two crests meeting: heights add up = bigger wave.
Occurs when path difference = nฮป (whole number of wavelengths)
When two waves combine to produce a resultant wave with smaller amplitude than either individual wave.
A crest and trough of equal size meeting: they cancel out = zero displacement.
Occurs when path difference = (n+ยฝ)ฮป
The spreading out of a wave as it passes through a gap or around an obstacle.
Sound bends around corners โ you can hear someone in the next room even when they're not visible.
Diffraction is greatest when the gap size is similar to the wavelength.
When the vibrations of a transverse wave are confined to a single plane.
Polaroid sunglasses block glare by only allowing light vibrating in one plane to pass through.
Only transverse waves can be polarised. Sound (longitudinal) cannot.
A wave pattern formed when two waves of equal frequency and amplitude travel in opposite directions, superposing to produce nodes and antinodes.
A vibrating guitar string: the wave bounces back from the bridge and nut, and the two waves create a stable standing wave pattern.
No net energy transfer in a standing wave.
A point on a standing wave that remains stationary (zero displacement).
The fixed ends of a vibrating string are nodes.
A point on a standing wave that experiences maximum displacement.
The middle of a vibrating guitar string is an antinode โ it vibrates the most.
The lowest frequency at which a body can vibrate naturally โ corresponds to the longest standing wave (1 antinode, 2 nodes).
Also called the first harmonic.
Integer multiples of the fundamental frequency. The first harmonic = f, second = 2f, etc.
f = 1st harmonic. 2f = 2nd harmonic (= 1st overtone).
Frequencies above the fundamental. The 1st overtone = 2f, 2nd overtone = 3f, etc.
1st overtone = 2nd harmonic. The naming differs โ know both.
The apparent change in frequency of a wave due to the relative motion between the source and observer.
An ambulance siren sounds higher in pitch as it approaches (waves compressed) and lower as it moves away (waves stretched).
Moving towards = higher frequency. Moving away = lower. Applies to sound and light.
When a body is forced to vibrate at its own natural frequency, producing large-amplitude oscillations.
A wine glass can shatter if a singer hits its resonant frequency โ energy transfers efficiently into the glass.
Occurs when driving frequency = natural frequency.
The power carried by sound waves per unit area perpendicular to the direction of propagation.
A measure of sound intensity relative to the threshold of hearing, measured in decibels (dB).
The minimum intensity audible to the human ear at 1000 Hz. Value: 1ร10โปยนยฒ W/mยฒ.
Iโ = 1ร10โปยนยฒ W/mยฒ. Used as reference level for dB scale.
The full range of electromagnetic waves ordered by frequency (or wavelength). From lowest to highest frequency: radio, microwave, IR, visible, UV, X-rays, gamma rays.
All in the family of EM waves, all travel at c in a vacuum.
ROY G BIV for visible light. Radio โ Gamma = increasing frequency, decreasing wavelength.
The separation of different wavelengths of light by a prism or diffraction grating, since different wavelengths travel at different speeds in a medium.