Wave Motion Topic

Transverse Pulses and Wave

Concept 3 demos

Lecture hall viewed from the back rows, with white plastic tubing hanging from the upper balcony railing and curving down toward the front of the room

Transverse Waves

Demonstrates transverse wave pulses, fixed-end reflection with phase inversion, constructive and destructive interference, and standing wave formation using a long plastic tube stretched across the lecture hall.

Close-up of the upper portion of the torsional wave machine, showing horizontal rods with white end-balls attached to a vertical wire, mounted to a catwalk bracket above the lecture hall

Torsional Wave Machine

Demonstrates torsional wave propagation along a vertical cable with perpendicular rods. Students observe pulse propagation, reflection with phase reversal at a fixed boundary, and superposition of incident and reflected waves.

Pendulum wave apparatus photographed mid-swing from below, showing steel balls on bifilar suspension at progressively different lengths

Pendulum Waves

An array of pendulums with harmonically related lengths cycles through striking patterns of coherence and apparent chaos over a 54-second period. Demonstrates beat phenomena, phase relationships, and the superposition of …

Longitudinal Pulses and Waves

Concept 3 demos

Metal slinky suspended by strings from a horizontal rod between two ring stands on a lecture bench, with one end clamped to the stand

Suspended Slinky Waves

A slinky suspended by strings across the lecture bench demonstrates longitudinal and transverse wave propagation, reflection from fixed and free ends, and how viewing angle affects wave visibility.

Plastic Slinky threaded on a meter stick between two bench clamp stands at eye level, in front of a chalkboard

Longitudinal Wave

Demonstrates longitudinal wave pulses in a Slinky, showing compressions and rarefactions traveling parallel to the wave direction. Helps students distinguish longitudinal from transverse waves and see that individual coils oscillate …

Three views of the air track compression wave apparatus: two wide shots showing the full track on a lecture bench with pucks and rubber bands, and a close-up of the air supply connection and support structure

Compression Wave Demonstration

Rubber-band-coupled pucks on an air track show longitudinal compression wave propagation and reflection in a discrete medium. Provides a visible analog to sound waves in air.

Standing Waves

Concept 2 demos

Rope stretched across the full length of the lecture bench, with motor driver at the far left end and pulley assembly with hanging mass at the right end

Standing Waves on Rope

A motor-driven rope stretched across the lecture bench displays standing wave patterns at resonant frequencies. Students observe nodes, antinodes, and harmonics, and see how changing tension shifts the resonance frequencies.

Standing wave lantern slide shown at two different handle positions: each view shows three sinusoidal wire traces — two traveling waves (top two) and their standing-wave superposition (bottom)

Standing Waves

A rotating overhead-projector slide animates two traveling waves moving in opposite directions and displays their superposition as a standing wave. Students see directly that standing waves are not a separate …

Impedance and Dispersion

Concept 1 demo

Composite of four photos showing standing waves at successive harmonics in a nonuniform rope stretched across a lecture bench, with the motor driver on the left and pulley assembly on the right

Standing Waves in Nonuniform Rope

Demonstrates that wave velocity depends on the linear mass density of the medium. Two ropes of different thickness, joined and driven at the same frequency, show different wavelengths — the …

Compound Waves

Concept 1 demo

Wave addition apparatus with red and green beads on vertical rods forming a sine wave, with the larger solid wave template inserted at the base

Wave Addition

Demonstrates the superposition principle by mechanically adding two sine waves. Students observe constructive and destructive interference, and see how combining waves of different wavelengths produces complex waveforms.

Wave Properties of Sound

Concept 2 demos

Glass bell jar on round vacuum platform with Energizer battery, buzzer with metal bell, and red wire clip, sitting on a wooden disc spacer; vacuum valve visible at base

Bell in Vacuum

Demonstrates that sound requires a medium for propagation. As air is evacuated from a bell jar containing a buzzer, the sound diminishes to near-silence, then returns when air is readmitted.

Brown helium cylinder secured on a green wheeled cart with brass Victor regulator, clear flow meter tube, and flexible tubing at top

Helium Tank

Inhaling helium and speaking demonstrates how the speed of sound depends on gas density. The higher sound velocity in helium shifts vocal tract resonances (formants) upward, producing the characteristic "chipmunk" …

Phase and Group Velocity

Concept 1 demo

Two overlapping transparency sheets with vertical black lines at 90% and 100% line density, showing subtle beat pattern

Group Velocity

Superimposing two transparency sheets with different line spacings creates a beat pattern (moire effect). When one sheet slides across the other, the beat pattern moves much faster than the sheet …

Doppler Effect

Concept 4 demos

Blue and green hollow Nerf ball with circular openings; a battery-powered buzzer circuit is visible inside through the holes

Doppler Effect Foam Ball

Students hear the Doppler shift directly as a buzzing ball is tossed back and forth, experiencing how relative motion between source and observer changes perceived pitch. The effect is immediately …

Orange foam ball wrapped in blue netting with attached clip and white string coiled on green surface, containing internal buzzer for Doppler effect demonstration

Doppler Effect Whirling Ball

Students directly hear the Doppler frequency shift from a buzzing ball whirled overhead. The pitch rises as the ball approaches and falls as it recedes, giving intuitive access to how …

Two aluminum I-beam tuning forks: a smaller beam with a string loop (left) and a larger beam suspended from a ring clamp on a bench clamp stand (right), in front of a chalkboard

Doppler Effect I-Beams

Two identical I-beam tuning forks produce slow (or no) beats when stationary. Swinging one beam toward and away from the class changes the beat frequency via the Doppler shift, giving …

Shock Waves

Concept 1 demo

Black braided leather bullwhip coiled on green surface, with cylindrical handle and braided knot, tapering from thick braid to flat ribbon at the tip

Bullwhip

The bullwhip tapers from a one-inch handle to a thin ribbon over 9.5 feet. A loop sent down the whip accelerates as mass per unit length decreases, reaching supersonic speed …

Interference and Diffraction

Concept 2 demos

Top: a single transparency showing concentric semicircular rings representing wavefronts from one source. Bottom: two transparencies overlapped with centers offset, producing a moiré interference pattern with hyperbolic bright and dark fringes.

Moiré Patterns

Visualizes two-source wave interference using overlapping transparencies printed with concentric rings. Students observe how moiré fringes representing constructive and destructive interference change as the "source" separation varies.

Projected transparency showing two side-by-side diagrams of double-slit interference. Each diagram has two point sources at the bottom with circular wavefronts, sinusoidal wave patterns along two paths converging at a screen (horizontal bar) at top. The left and right panels show different phase alignments at the screen.

Wave Interference Transparency

Demonstrates constructive and destructive interference in a double-slit geometry using a projected transparency. Students see how path difference from two coherent sources determines where maxima and minima appear on a …

Interference and Diffraction of Sound

Concept 4 demos

Agilent 33120A function generator on the lecture hall AV island, with BNC cable connected to the front panel output and RCA audio inputs visible on the AV system below

Two Source Sound Interference

Two speakers driven by a single function generator create an interference pattern that students explore by moving through the room. Students experience constructive and destructive interference directly, connecting path length …

Two Source Sound Interference, Oscillating

Two speakers driven in phase on a rotating bar create a spatial interference pattern that sweeps across the room. Students hear alternating loud and quiet regions, directly experiencing constructive and …

Wooden-framed box with glass panel containing two sinusoidal wire shapes, offset so peaks of one align with troughs of the other. Sliding handle visible on left.

Interference Lantern Slide

Visually demonstrates constructive and destructive interference using two overlapping wire sinusoids on a sliding mechanism. Moving the handle shifts one wave relative to the other, showing in-phase reinforcement and out-of-phase …

Beats

Concept 4 demos

Two black metal vibraphone bars labeled A441 and A440, mounted vertically on a wooden base with orange felt pads at the nodes and red felt dampers on top, with a wooden mallet in front

Vibraphone Bars

Demonstrates acoustic beats — the periodic rise and fall of loudness when two nearly identical frequencies sound together. Two vibraphone bars tuned to 440 Hz and 441 Hz produce clearly …

Two aluminum rods mounted vertically in finger clamps on right-angle clamps attached to a bench clamp rod at a table edge, with a small hammer resting in the assembly

Singing Rod Beats

Two aluminum rods differing by 2 mm in length produce nearly identical tones that beat at ~3 Hz when struck simultaneously. Students hear the amplitude modulation directly and connect it …

Two glass whistles connected by brass fittings and wire, paired to produce slightly different frequencies

Quincke's Tubes

Two glass whistles with slightly different frequencies produce audible beats when blown simultaneously. Students hear the periodic amplitude modulation directly and can verify that by counting beats per second.

Coupled Resonators

Concept 2 demos

Two matched tuning forks mounted on wooden resonance boxes; the right fork has adjustable slider weights on its prongs. A rubber mallet sits in front.

Sympathetic Resonance

Demonstrates sympathetic resonance: striking one tuning fork excites a matched fork on a nearby resonance box through acoustic coupling. After damping the struck fork, students hear the second fork vibrating …

Tuning fork in wooden base at resonance: orange and white ping pong balls suspended from a horizontal rod are motion-blurred as they bounce off the vibrating tines. Speaker visible at base of fork, signal generator at right.

Driven Tuning Fork

Demonstrates mechanical resonance by driving a 256 Hz tuning fork with a speaker at various frequencies. Ping pong balls resting against the tines bounce vigorously at the resonant frequency and …