Below is a concise list of key definitions from Chapter 12: Acoustics

Below is a concise list of key definitions from Chapter 12: Acoustics of the 11th Class Physics syllabus for the Federal Board of Intermediate and Secondary Education (FBISE), aligned with the National Book Foundation (NBF) curriculum. These definitions cover the essential concepts related to acoustics as typically presented in this chapter.

1. Acoustics: The branch of physics that studies the production, propagation, and perception of sound.
2. Sound: A mechanical longitudinal wave that propagates through a medium, causing variations in pressure and density, perceivable by the human ear.
3. Longitudinal Wave: A wave in which the particles of the medium vibrate parallel to the direction of wave propagation, as in sound waves.
4. Compression: A region in a sound wave where particles are closest together, resulting in high pressure.
5. Rarefaction: A region in a sound wave where particles are farthest237. Simple Harmonic Motion (SHM): A type of periodic motion where the restoring force is directly proportional to the displacement and acts opposite to it, described by F = -kx. apart, resulting in low pressure.
6. Wavelength (λ): The distance between two consecutive compressions or rarefactions in a sound wave, measured in meters.
7. Frequency (f): The number of sound wave cycles passing a point per unit time, measured in hertz (Hz), determining pitch.
8. Time Period (T): The time taken for one complete cycle of a sound wave, given by T = 1/f, measured in seconds.
9. Amplitude (A): The maximum displacement of particles in a sound wave from their equilibrium position, determining loudness.
10. Speed of Sound (v): The speed at which sound waves propagate through a medium, given by v = fλ, dependent on the medium’s properties.
11. Pitch: The perceptual quality of sound determined by its frequency; higher frequency corresponds to higher pitch.
12. Loudness: The perceptual intensity of sound, related to the amplitude of the sound wave, measured in decibels (dB).
13. Intensity (I): The power carried by a sound wave per unit area, given by I = P/A, measured in watts per square meter (W/m²).
14. Decibel (dB): A logarithmic unit used to measure sound intensity level, given by β = 10 log₁₀(I/I₀), where I₀ is the reference intensity (10⁻¹² W/m²).
15. Audible Range: The range of frequencies detectable by the human ear, typically from 20 Hz to 20,000 Hz.
16. Infrasound: Sound waves with frequencies below the audible range (<20 Hz).
17. Ultrasound: Sound waves with frequencies above the audible range (>20,000 Hz), used in medical imaging and other applications.
18. Doppler Effect: The change in frequency or pitch of a sound wave observed when the source and observer are in relative motion.
19. Shock Wave: A high-pressure wave produced when an object moves faster than the speed of sound in a medium, creating a sonic boom.
20. Resonance: The amplification of sound when an object vibrates at its natural frequency due to an external sound wave of the same frequency.
21. Fundamental Frequency: The lowest frequency at which a system (e.g., a string or air column) vibrates, also called the first harmonic.
22. Harmonics: Integer multiples of the fundamental frequency, producing distinct sound patterns in vibrating systems.
23. Stationary Waves in Pipes: Standing sound waves formed in open or closed pipes, producing specific frequencies based on pipe length.
24. Open Pipe: A pipe open at both ends, with a fundamental frequency given by f₁ = v/2L, where v is the speed of sound and L is the pipe length.
25. Closed Pipe: A pipe closed at one end, with a fundamental frequency given by f₁ = v/4L, producing only odd harmonics.
26. Beats: The periodic variation in loudness caused by the interference of two sound waves with slightly different frequencies.

These definitions encapsulate the core concepts of acoustics from Chapter 12 of the FBISE 11th Class Physics curriculum. If you need further explanation or additional terms, please let me know!