Edexcel IGCSE Physics Chapter 14 : Sound

Prepared By: Shakil Raiman

14.1 What is sound?

Sound waves are longitudinal waves Sound waves are produced by vibration of

objects.

Here the loudspeaker vibrate and produce sound.

14.1 What is sound?

As the speaker cone moves to the right it pushes air molecules closer together, creating a compression.

The region where the particles are spread out is called rarefaction.

14.2 Travelling of Sound Wave Sound wave needs

medium to travel. It can travel through

solid, liquid and gas (air)

It cannot travel through vacuum.

14.3 Speed of Sound

In air : 330 m/s In water: 1500 m/s In Steel: 5000 m/s

14.4 Factors Affecting the Speed of Sound in Air:

Temperature: If temperature increases speed of sound increases.

Humidity : If humidity increases speed of sound increases.

Air Flow: If air flow in the direction of sound flow speed of sound increases.

Altitude: At high altitude speed of sound is less. Pressure does not affect the speed of sound.

14.5 Echo and Reverberation When sound wave strikes a surface it

may be reflected. A reflected sound wave is called an echo.

Multiple echo is called reverberation. It causes problem while sound is played in hall rooms or auditoriums. So, the walls of the hall rooms or auditoriums are covered with soft materials to decrease the reverberation.

14.6: Echo Sounding

Echo is used to measure the depth of the sea or shoal of fish by the ship which is called echo sounding.

V=2d/t

14.7: Diffraction

The bending of waves while passing through narrow gaps (or at the edges of an obstacle) is called diffraction.

Waves diffract more when width of the gap is close to the wavelength of the wave.

14.8 Diffraction of Sound

As sound is wave it can be diffracted..

14.9: Audible Range

Different creature has different audible range.

Human Audible Range is 20Hz to 20,000 Hz Sound waves with frequency less than 20Hz

is called infrasound. It is used for seismic survey.

Sound waves with frequency more than 20,000Hz is called ultrasound. It is used for ultrasonography or cleaning.

14.10: Loudness, Pitch and Quality:

The greater the amplitude of the vibration the louder the sound.

The higher the frequency of the vibration the higher the pitch.

Thank You All

Wish you all very good luck and excellent result.