general wave properties

Question 1

Define “wave”

Answer 1

A propagation of a disturbance which carries energy from one point in space to another without the transfer of matter

Question 2

Distinguish between progressive and stationary waves

stationary waves not really in syllabus

Answer 2

progressive: transfers energy from the a source without the transfer of matter
stationary: waves whereby energy is not transferred

mechanical + em waves are progressive waves in nature

Question 3

Distinguish between mechanical and EM waves

Answer 3

mechanical: produced in deformable or elastic medium, requiring a material medium to be transmitted
EM: do not require a medium for transmission and travel in vacuum at the speed of light, 3.0 * 10^8 m/s

Question 4

Distinguish between tranverse and longitudinal waves

Answer 4

tranverse: direction of particles’ oscillation is such that its displacement will be perpendicular to direction of energy transfer
longitudinal: direction of particles’ oscillation is such that its displacement will be parallel to direction of energy transfer

Question 5

State the function of a displacement-distance graph

Answer 5

shows displacement of all particles along path of propogation at various distances away from source at an instance of time

Question 6

Define displacement of a particle

Answer 6

distance in a specified direction from its equilibirium position

Question 7

Define amplitude of the wave

Answer 7

magnitude of maximum displacement of particle from equilibrium position

Question 8

Define wavelength

Answer 8

shortest distances between 2 points vibrating in phase
or
shortest distance between 2 crests/troughs (depends on the question to write this)

Question 9

State the function of a displacement-time graph

Answer 9

shows displacement of a single particle along the path of propogation at various times

Question 10

Define period

Answer 10

time for a particle of the wave to complete one cycle of vibration

Question 11

Define frequency

Answer 11

number of complete waves produced per second (unit = Hz)

Question 12

Define wavefront

Answer 12

imaginary line or surface that join points of a wave that are in phase

Question 13

Distinguish between crest and trough

Answer 13

crest: highest point of a wave
trough: lowest point of a wave

Question 14

State the formula for frequency

Answer 14

f = 1 / T
OR
f = number of oscillations / time

Question 15

State the formula(e) for wave speed

Answer 15

v = λ / T
OR
v = fλ

Question 16

Define wave speed

Answer 16

distance travelled by a wave per second

Question 17

State the types of waves that sound is

Answer 17

progressive, mechanical, longitudinal

Question 18

Explain how a vibrating object produces sound and how these waves are transmitted in the air

Answer 18

1. when an object vibrates, it alternatively pulls and pushes air molecules near it, causing them to oscillate at the same frequency
2. sound is then propagated through air by the vibration of air molecules in direction parallel to direction of wave propagation
3. as air molecules vibrate about their equilibrium positions, they collide with neighbouring particles
4. transferring energy from one particle to another until the (something)

Question 19

How do you distinguish between compressions and rarefactions on a displacement-distance graph? (assuming positive displacement = right)

Answer 19

compression: particle to the left has positive displacement, particle to the right has negative displacement
rarefaction: particle to the left has negative displacement, particle to the right has positive displacement

Question 20

Pressure-distance graph is how many degrees out of phase with displacement-distance graph?

Answer 20

90°

Question 21

Define echo

Answer 21

repetition of sound due to reflection of sound

Question 22

Explain how pitch varies with tension, length, and thickness/mass per unit length of string

Answer 22

more taut = higher pitch
shorter = higher pitch
thinner = higher pitch

Question 23

What is ultrasound?

Answer 23

sound with frequencies above the upper hearing limit of the human range of audability (20 ~ 20 000 Hz)

Question 24

Ultrasound can be used to measure sea depth. When the sea is beyond a certain depth, pulses from the ship cannot be send out too often. Explain why.

Answer 24

reflected pulses may coincide with or appear after subsequent pulses sent from the ship, affecting data interpretation

Question 25

Explain how ultrasound scanning works for an unborn baby

Answer 25

ultrasound travels freely through soft and fluid tissues but echoes when it hits denser surfaces.
reflected waves are picked up by probe/detector and relayed to machine

Question 26

Explain how an object (e.g. ping pong ball) can be used to determine the type of wave of a water wave

Answer 26

Place it on the water and observe its motion
It oscillates up and down perpendicular to direction of wave travel at the same location
Shows that water molecules are not moving along the wave but rather vibrating up and down about their equilibrium positions.
Hence, water wave is a tranverse wave

Question 27

Explain how sound can be used to detect impurities

Answer 27

an echo received due to sound bouncing off cracks indicate impurities

Question 28

Explain 2 advantages of using sound to detect impurities over gamma rays

Answer 28

1. typically doesn’t have health hazards
2. gamma ray is too penetrative and penetrates through the structure without detecting cracks/faults