KERALA PSC / PHYSICS / SOUND / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

 

KERALA PSC / PHYSICS / SOUND / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

KERALA PSC / PHYSICS / SOUND / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

·      Sound waves are longitudinal waves

·      Sound is a travelling wave

·      Sound requires medium to travel

·      Sound cannot travel through vacuum

·      Study of sound is known as Acoustics

·      Echo and reverberation are due to the reflection of sound. For the production of echo there should be a minimum distance of 17m between us and the reflecting surface.

·      Bats can fly in the dark because they can generate ultrasonic sound and if there is any hindrance in their way the sound waves get reflected and they can change their direction. They use this method to catch insects also

·      Since sound waves need a medium to travel they cannot be transmitted through vacuum.

·      The audible frequency of human ear is between 20 hertz and 20000 hertz (20 KHz)

·      330 m/s is roughly 750 miles per hour. Most aero planes have speeds less than this ie, less than speed of sound in air. If the speed is greater than this, it is said to be supersonic speed. The ratio of this speed to that of sound is called Mach number.

·      Velocity of sound in the air is 340 m/s

·      Sound consists of waves of alternate compression and rarefaction that transmit kinetic energy through a medium.

·      Frequency of a sound wave is the number of wavelengths (vibrations) that are completed in a given period of time.

·      Doppler effect is the change in a sound wave’s frequency (and wavelength) that is caused when the hearer and sound source move relative to each other.

·      Sounds are distinguished from each other by pitch (frequency), loudness (intensity) and quality.

·      We can recognize our friends from their voices due to the quality of sound

·      Phonogram is a machine to reproduce sound

·      The speed of sound depends on the medium the waves pass through

·      Sounds with frequencies lower than the lowest limit of human hearing (about 20 Hz) are called infrasonic waves

·      Sounds are frequency higher than 20000 Hz are known as ultrasonic and are inaudible.

·      SONAR stands for Sound Navigation and Ranging. It uses ultrasonic waves.

·      The velocity of sound is maximum in solids and least in gases. Velocity of sound in moist air is greater than in dry air.

·      The intensity of sound is measured in decibel.

·      The intensity of polite conversation is 40db – 30db

·      During night the allowed intensity of sound in a hospital area is 40 db.

·      The normal level of sound is 60 to 120 db. The sounds of frequencies more than 20000 Hz are called as Ultrasonic sounds

·      The reverberation of sound in a hall results due to continued reflection.

·      Sound travels faster in steel

·      Ultrasonic sounds can be received and emitted by bats, while infrasonic sounds can be received by snakes.

·      Equipment for generating or using sound includes musical instruments, hearing aids, sonar systems and sound reproduction and broad casting equipment. Many of these use electro-acoustic transducers such as microphones and loud speakers.

     

KERALA PSC / PHYSICS / SOUND / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES