Waves

Question 1

purpose of waves

Answer 1

to transport energy

Question 2

longitudinal waves

Answer 2

particles of medium vibrate/ oscillate in the same direction as the energy travels

Question 3

transverse waves

Answer 3

particles of medium vibrate/ oscillate at right angles to the direction of travel of the wave

Question 4

amplitude

Answer 4

the maximum extent of a vibration or oscillation

Question 5

crest

Answer 5

a point on wave with the maximum value/ highest point of upward displacement within a cycle

Question 6

trough

Answer 6

a lowest point on wave with the minimum value of downward displacement within a cycle

Question 7

transverse wave wavelength

Answer 7

minimum distance in which a wave repeats itself

Question 8

frequency

Answer 8

number of waves that pass a point every sec (hertz)

Question 9

period

Answer 9

time for one complete wave

Question 10

the wave equation

Answer 10

wave speed = frequency x wavelength

frequency=1/time period

Question 11

conclusion for slinky experiment:
the longer the slinky is stretched…

Answer 11

the faster the wave speed of a pulse travels along the slinky

Question 12

conclusion for pendulum experiment:
the long the length of the pendulum…

Answer 12

the greater the time period, but the rate decreases slowly

Question 13

what are sound waves?

Answer 13

vibrating air molecules

Question 14

how many hertz can the human ear typically hear?

Answer 14

from 20hz-20000hz

Question 15

what are sounds 20000+ hz called?

Answer 15

ultrasonic

Question 16

for longitudinal waves, what does a high pitch result in the shape of the wave?

Answer 16

high frequency (distance between waves closer)

Question 17

for longitudinal waves, what does a loud sound result in the shape of the wave?

Answer 17

large amplitude (height of the wave larger)

Question 18

speed of sound in air

Answer 18

340m/s

Question 19

things that have transverse waves

Answer 19

radio, infra red, water, skipping rope, guitar string

Question 20

things that have longitudinal waves

Answer 20

sound

Question 21

what surface reflect sounds better and what absorb sounds better? which one makes noise sound clearer?

Answer 21

polished surfaces; soft object surfaces; soft object surfaces

Question 22

what is ultrasound?

Answer 22

sound waves of frequencies greater than 20000hz, above the upper limit of the hearing range for humans

Question 23

how are ultrasounds made?

Answer 23

made by electronic systems which produce electrical oscillations which are used to generate the ultrasonic waves

Question 24

uses of ultrasonic waves

Answer 24

• pre-natal scanning
• echo-sounding
• cleaning delicate objects
• detecting flaws and cracks
• echo-location by bats

Question 25

how does ultrasonic waves work for pre-natal scanning, echo-sounding, detecting flaws and cracks?

Answer 25

time delay of reflections can be used to calculate the depth of/ size of and distance to the reflecting surface

Question 26

how does ultrasonic waves work for cleaning delicate objects? what benefits does this have?

Answer 26

the vibrations of the ultrasonic waves dislodge dirt particles from the surface of the object, ensuring that there’s no danger of breakage or need to disassemble the object

Question 27

why is it important to have a very narrow beam of ultrasound waves?

Answer 27

it gives us a focused detailed image

Question 28

what is resonance frequency?

Answer 28

when the driving frequency equals the natural frequency of an object, the oscillations become larger

Question 29

4 layers in earth’s structure

Answer 29

crust, mantle, outer core, inner core

Question 30

primary waves (p waves) characteristics

Answer 30

longitudinal and faster (6km/s), can travel through all air, liquid and rock

Question 31

secondary waves (s waves) characteristics

Answer 31

transverse and slower (4km/s), can only travel through solids

Question 32

longitudinal wave compression

Answer 32

a region in a longitudinal wave where the particles are closest together

Question 33

longitudinal wave rarefaction

Answer 33

a region in a longitudinal wave where the particles are furthest away

Question 34

longitudinal wave wavelength

Answer 34

length between two points of compression or two points of rarefaction

Question 35

why do the paths of the waves bend as they travel through the earth?

Answer 35

because there are changes in composition, pressure and temperature within the layer of the earth so they travel at different speeds though different materials

Question 36

why is there an s wave shadow zone?

Answer 36

because s waves can’t travel through anything not solid

Question 37

what does the shadow zone tell us about the earth’s structure?

Answer 37

the earth has a solid mantle and a liquid core

Question 38

how can tall buildings be made earthquake proof?

Answer 38

flexible foundations, damping, vibration deflection technology, shear walls, cross braces, diaphragms and moment-resisting frames

Question 39

explain how resonance is related to the height of a building during an earthquake

Answer 39

taller buildings tend to experience more prolonged and sustained shaking than shorter ones because they often have lower damping naturally, meaning that they don’t restrain or reduce energy of vibratory motion and amplitude of oscillations that much