chapter 12 - sound

Question 1

define compression

Answer 1

it is a region where the particles are closer together and the air pressure is higher than the surrounding air pressure

Question 2

define rarefraction

Answer 2

it is a region where the particles are further apart and the air pressure is lower than surrounding air pressure

Question 3

how is sound propagated?

Answer 3

in the form of longitudinal waves

Question 4

describe how sound is transmitted from the source to the receiver in air

Answer 4

when the vibrating source moves forward, a compression is formed in the air

when it moves backwards, a rarefaction is formed in the air

the air molecules vibrate continuously and produces a series of alternating compressions and rarefactions to travel outwards and propagate through the air towards the receiver

the direction of vibration of the air particles is parallel to the direction the wave travels as sound is a longitudinal wave

Question 5

what affects the pitch of a sound?

Answer 5

the frequency of the sound

Question 6

what affects the loudness of a sound?

Answer 6

the amplitude of the sound

Question 7

state the range of audible frequencies that can be detected by the human ear

Answer 7

20Hz to 20kHz

Question 8

name two animals that have a higher audible limit than human beings

Answer 8

dogs and bats

Question 9

frequency of ultrasound

Answer 9

greater than 20kHz

Question 10

frequency of infrasound

Answer 10

lesser than 20Hz

Question 11

state the speed of sound in air

Answer 11

340m/s

Question 12

in which medium - solid, liquid or gas, does sound travel the fastest?

Answer 12

solids - the particles in solids are closely packed

Question 13

what is a echo?

Answer 13

when the reflected sound and the direct sound can be heard as separate sounds, the reflected sound is known as an echo

Question 14

what is the ideal nature of the reflecting surface in order to obtain a distinct echo?

Answer 14

large, hard, smooth surfaces which is far enough

Question 15

state how sound waves and light waves are similar

Answer 15

energy is transmitted in both
both can be reflected

Question 16

state how sound waves and light waves are different

Answer 16

• direction of vibration
  (the direction of vibration of sound waves is parallel whilst it is perpendicular to wave motion in light waves)
• type of wave
  (sound waves are longitudinal waves but light waves are transverse waves)
• transmission in vacuum
  (sound waves cannot be transmitted in vacuum whilst light waves can)
• speed in air
  (sound waves speed in air is 330ms-1 whilst light waves speed in air is 3x10^4)