Mechanical Oscillations and Waves

Question 1

what are mechanical waves generated by

Answer 1

vibrating sources

Question 2

what is the only way that mechanical waves can travel

Answer 2

if they are travelling through a medium

Question 3

what is a longitudinal wave

Answer 3

• a wave in which the particles oscillate left and right

- parallel to the direction of the waves motion

Question 4

what is a transverse wave

Answer 4

• a wave in which the particles oscillate up and down

- perpendicular to the direction of the waves motion

Question 5

where would the compression of a longitudinal wave be

Answer 5

where the oscillating particles of the wave come close together or compress

Question 6

where would the refraction of a longitudinal wave be

Answer 6

where the oscillating particles of the wave move away from each other or are more spread out

Question 7

what kind of wave is sound

Answer 7

a longitudinal wave

Question 8

what experiment is carried out to prove this with a loudspeaker connected to a generator and a candle flame

Answer 8

• place the flame close to the loudspeaker set to 50Hz or less
• the candle flame should be seen to flicker back and forth by the oscillating air molecules

Question 9

why would the flame flicker back and forth and what is the common false explanation for this

Answer 9

• it is wrong to think that the sound wave is pushing the flame as it travels
• it is the oscillations of the air molecules that move back and forth about a mean fixed position

Question 10

what do areas of compression and rarefaction create

Answer 10

• compressions create areas of high pressure

- rarefactions create areas of low pressure

Question 11

why are the ripples of a still body of water after something has been dropped in it a good example of how a longitudinal wave behaves

Answer 11

• the ripples move outwards, correctly showing the movement of the wave from the source
• the points where the wave is high and low represent the compressions and rarefactions of a longitudinal wave

Question 12

what would the movement of an object floating on the surface of the body of water be due to the ripples

Answer 12

the object would move up and down and not move away or towards the source

Question 13

what are the three properties of an oscillation

Answer 13

• frequency, f
• amplitude, A
• period, T

Question 14

what are the definitions of amplitude, frequency and period

Answer 14

• amplitude is the maximum displacement from the mean position
• period is the time taken for one complete oscillation
• frequency is the number of complete oscillations per second

Question 15

what are the units of them

Answer 15

• amplitude = metres (m)
• period = seconds (s)
• frequency = hertz (Hz)

Question 16

what is the equation showing the relationship between frequency and periods

Answer 16

f = 1/T