Waves and Sound- Physics | General Science

Sound as a form of energy, requires a medium (solid, liquid, or gas) doesn’t travel in vacuum. transferring the disturbance through the medium in the form of a wave.

There are two types of waves:

• Longitudinal waves: Particles oscillate parallel to wave direction (e.g., sound waves). Sound waves are mechanical longitudinal waves. Sound travels faster in solids, slower in gases.
• Transverse waves: Particles oscillate perpendicular to wave direction (e.g., water waves).

Wave Characteristics of Sound:

• Compression and Rarefaction: Sound waves are made of compressions (high pressure/density) and rarefactions (low pressure/density).
• Wavelength (λ): Distance between two consecutive compressions or rarefactions.
• Amplitude (A) (loudness): Maximum disturbance from the mean position.
• Frequency (ν) (pitch): Number of oscillations per second. Measured in hertz (Hz).
• Time Period (T): Time taken to complete one oscillation. v = 1/T​

Pitch and Loudness:

• Pitch is related to frequency: Higher frequency = Higher pitch.
• Loudness depends on amplitude. Larger amplitude = louder sound.

Quality and Timbre:

• Tone: Pleasant sound of single frequency.
• Note: Sound made of multiple frequencies, musical.
• Noise: Unpleasant, irregular sound.
• Timbre: Quality that helps distinguish two sounds with same pitch and loudness.

Speed of Sound

• Depends on the medium: v = λ × v (Speed = Wavelength × Frequency)
• Speed of sound is determined by the medium and its temperature.

Reflection of Sound

• Like light, sound reflects from surfaces, obeying the laws of reflection. Angle of incidence = angle of reflection.
• Echo is reflected sound heard after 0.1s. Minimum distance for echo: 17.2 meters.
• Reverberation, Repeated reflection of sound causing persistence. Unwanted in auditoriums; reduced using sound-absorbing materials.
• megaphones, horns, stethoscopes use sound reflection. Concert halls have curved ceilings to spread sound evenly.

Range of Hearing

• Below 20 Hz: Infrasonic (e.g., elephants, earthquakes).
• Human hearing range: 20 Hz to 20,000 Hz.
• Above 20 kHz: Ultrasonic (e.g., dolphins, bats, moths).

Applications of Ultrasound

• Cleaning: Used for cleaning intricate items like electronic components, spiral tubes, etc., by dislodging dirt via high-frequency waves in a solution.
• Flaw Detection: Used to detect internal cracks or holes in metal blocks. Ultrasonic waves reflect back from defects, revealing their presence.
• Echocardiography: Reflecting ultrasound from the heart to form an image.
• Ultrasound Imaging (Scanning): Used to view internal organs like liver, kidney, gall bladder, uterus, etc. Helps detect stones and tumors by reflecting waves from tissue boundaries.

Human voice is produced due to vibrations in vocal cords. Hearing Aid is An electronic device used by people with hearing loss. It consists of a microphone, amplifier, and speaker.