Waves

An example of longitudinal waves in gas as a medium is sound waves.

• When a sound source vibrates, it causes the gas molecules next to it to compress and expand, creating regions of higher and lower pressure (compressions and rarefactions).
• These pressure variations propagate through the gas as a longitudinal wave, where the particles of the medium oscillate parallel to the direction of wave travel.

Sound waves are longitudinal mechanical waves.

Longitudinal Waves:
In these waves, the particles of the medium vibrate parallel to the direction the wave travels. Think of a slinky being pushed and pulled at one end; the compression and expansion move along the slinky, and the coils move back and forth in the same direction. Sound waves in air cause air molecules to compress and expand along the direction of the sound's movement.

Mechanical Waves:
These waves require a medium (like air, water, or solids) to travel through. The vibrations are passed from one particle of the medium to the next. Sound cannot travel through a vacuum because there are no particles to vibrate.

So, sound waves propagate as a series of compressions (regions of higher pressure) and rarefactions (regions of lower pressure) moving through a medium.

TV remote controls primarily work on the principle of infrared (IR) waves.

1. The remote control contains a small light-emitting diode (LED) that emits infrared light, which is invisible to the human eye.
2. When you press a button on the remote, it sends a specific code as a series of pulses of infrared light.
3. The TV has an infrared receiver that detects these light pulses and interprets the code.
4. Based on the received code, the TV performs the corresponding action (e.g., changing the channel, adjusting the volume, turning on/off).

Some newer remote controls may use Bluetooth or radio frequency (RF) technology, which don't require a direct line of sight and have a longer range. However, infrared is still the most common technology used in TV remote controls.

• This reflected sound wave is heard as a distinct repetition of the original sound, provided there is a sufficient time delay between the original sound and the reflected sound.
• This delay is determined by the distance the sound wave travels to the reflecting surface and back.

A body produces sound only if it vibrates.

• Sound is a mechanical wave that originates from the vibration of an object.
• These vibrations cause the surrounding medium (like air, water, or solids) to also vibrate, creating pressure variations that propagate as sound waves.
• When these waves reach our ears, they cause our eardrums to vibrate, which our brain interprets as sound.
• Without vibration, there would be no disturbance in the medium and therefore no sound produced.

The study of the production and propagation of sound waves is called acoustics.

• Acoustics is a multidisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids, including vibration, sound, ultrasound, and infrasound.
•  It encompasses the generation, propagation, and reception of these waves, as well as their effects.

• Galton first generated them.
• These waves cannot be polarized, as they are longitudinal waves in which the particles of the medium vibrate parallel to the direction of propagation of the wave.
• These waves have short wavelengths and high frequencies, so their energy is also high.

• By recognizing them, the bat gets an idea of the distance and position of the prey.

When the speed of an object exceeds the speed of sound, it is said to be traveling at supersonic speed.

• The speed of sound in air at standard temperature and pressure is approximately 343 meters per second (about 767 miles per hour).
• Any object moving faster than this speed is considered supersonic.
• When an object travels at supersonic speed, it can create shock waves in the air, which can result in a loud "sonic boom" when they reach an observer.