Sound — Class 11 Maharashtra HSC Physics revision notes
A 6-page visual revision sheet for Sound, written for Class 11 Maharashtra HSC Physics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Sound in one look
a longitudinal wave that needs a medium, carries energy, and shifts pitch the instant something moves
Wave motion, and the two types
- mechanical waves need a material medium: water waves, string waves, sound
- EM waves need none at all, they cross vacuum
- a progressive wave carries energy and momentum outward
- the medium's own particles never travel along with it, they only oscillate
- waves split into two types by how particles move relative to the wave
- transverse: particles vibrate perpendicular to the wave's direction
- longitudinal: particles vibrate along the same line as the wave
- waves are doubly periodic: periodic in time (period T), periodic in space (wavelength λ)
- a wave travels outward until stopped by a boundary: a wall, a pond's edge, the medium's limit
Transverse vs longitudinal
- particles vibrate perpendicular to the wave's direction: crests, troughs
- needs elasticity of shape, travels through solids and liquid surfaces only
- can be polarised, vibration confined to one plane
- particles vibrate along the same line as the wave: compressions, rarefactions
- needs elasticity of volume, travels through solids, liquids, gases
- cannot be polarised, vibration and propagation share one direction
Page 1 of 6. The full sheet, all 6 pages, opens free in the app.
What this Sound sheet covers
- wave motion
- types of waves
- progressive wave
- longitudinal wave
- transverse wave
- Wave motion, and the two types
- Transverse vs longitudinal
- Transverse
- Longitudinal
- Wave speed, the basics
- speed, frequency and wavelength
- frequency is the reciprocal of period
- wave equation
- amplitude
- phase
- The progressive wave equation
- displacement of a particle at position x, time t
- a is amplitude, k is angular wave number
- ω is angular frequency, varphi is initial phase
- Speed of a transverse wave on a string
- tension T, mass per unit length m
- Newton's formula and Laplace's correction
- Newton, isothermal elasticity
- Laplace, adiabatic elasticity
- for air
- Speed of sound in air at NTP, Laplace's formula
- Factors affecting the speed of sound in air
- Superposition of waves
- Echo, reverberation and acoustics
- Minimum distance for a distinct echo
- sound must travel there and back in more than 0.1 s
- Timing an echo off a wall
- Sound reflection at work
- Bats
- Dolphins
- SONAR
- Medical ultrasound
- Qualities of sound
- The decibel scale
- loudness in bel
- loudness in decibel, the common unit
- threshold of hearing
- The Doppler effect
- Doppler formula, general form
- listener speed v_L, source speed v_s, sound speed v
- A siren approaching a stationary listener
- Symbols
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Physics chapter by chapter against your real exam dates and free hours, and when the plan reaches Sound the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.