PHYSICS — WAVES, SOUND, VIBRATIONS, PENDULUMS Review

Wave

the motion of a disturbance through a medium

Mechanical Wave

a wave that requires a material medium to travel through

Medium

the material through which a disturbance travels (ex: air, water)

Pulse Wave

a single, non‑periodic disturbance

Periodic Wave

a wave produced by repeated, periodic motion

Transverse Wave

a wave whose particles vibrate perpendicular to the direction of motion

Longitudinal Wave

a wave whose particles vibrate parallel to the direction of motion

Compression

region of a longitudinal wave with high density/pressure

Rarefaction

region of a longitudinal wave with low density/pressure

Crest

highest point above equilibrium

Trough

lowest point below equilibrium

Wavelength ((λ)

distance between two identical points on a wave (crest‑to‑crest or trough‑to‑trough)

Amplitude

maximum displacement from equilibrium

Frequency (f)

number of cycles per second (Hz)

Period (T)

time for one complete cycle

T = 1/f.

Wave speed (v)

v = fλ

Energy of a Wave

increases with amplitude

larger amplitude = more energy transferred

Superposition Principle

the method of adding displacements of overlapping waves

Constructive Interference

waves on the same side of equilibrium add to form a larger amplitude

Destructive Interference

waves on opposite sides of equilibrium subtract to form a smaller amplitude

Complete Destructive Interference

equal but opposite pulses cancel completely

Reflection at free boundary

wave reflects upright

Reflection at fixed boundary

wave reflects inverted

Standing Wave

pattern formed when two waves of same frequency, wavelength, and amplitude travel in opposite directions

Node

point of complete destructive interference

no movement

Antinode

point halfway between nodes with maximum amplitude

Sound Wave

a longitudinal mechanical wave caused by vibrating particles

Audible Range

20 Hz to 20,000 Hz

Pitch

depends on frequency

higher frequency = higher pitch

Ultrasonic Waves

very high frequency waves used for imaging (short wavelength)

Speed of sound

depends on medium

travels fastest in solids, slowest in gases

Sound Intensity

rate of energy flow through an area

Decibel (dB)

unit measuring relative sound intensity

Doppler Effect

change in frequency due to relative motion between source and observer

Resonance

when an object vibrates at its natural frequency due to another vibrating source

Natural Frequency

the frequency at which a system naturally vibrates

Simple Pendulum

mass on a string that swings back and forth in simple harmonic motion

Period of a pendulum

T = 2π√(L/g)

Pendulum Period depends on

string length (L) and gravity (g), NOT mass or amplitude

Amplitude (Pendulum)

maximum angular displacement from equilibrium

Period of a mass-spring system

T = 2π√(m/k)

Mass-spring period depends on

mass (m) and spring constant (k)

Which tuning fork sound travels faster?

Both travel at the same speed in the same medium

speed depends on medium, not frequency.

Why sound needs a medium

sound is a mechanical wave

requires particle collisions to transfer energy.

Doubling frequency on a string

wavelength halves; speed stays the same (depends on medium/tension)

Speed of sound formula

v = fλ

Electromagnetic wave speed

all EM waves travel at 3×10⁸ m/s in a vacuum