P5.1 - Wave Behaviour

Question 1

What is a wave? (2)

Answer 1

an oscillation that transfers energy (1) without transferring matter (1)

Question 2

how do sound waves transfer energy?

Answer 2

They transfer energy by the molecules vibrating and knocking into neighbouring molecules

Question 3

How do phones communicate ?

Answer 3

Using Electromagnetic waves (microwaves if ur being specific)

Question 4

define amplitude

Answer 4

the distance from the middle of a wave to the crest or trough

Question 5

Define Wavelength

Answer 5

distance from one peak (or trough) to the next peak (or trough) in m

Question 6

define time period

Answer 6

the time for one wave to pass a given point or the time for one complete oscillation in seconds (s)

Question 7

define frequency

Answer 7

the number of peaks passing a point per second (measured in Hz)

Question 8

What is a rarefaction?

Answer 8

A part of a longitudinal sound wave which has low pressure (wide bits - particles spread far apart)

Question 9

what is a compression?

Answer 9

a part of a longitudinal wave where the pressure is high

close together lines - because particles are squashed together

Question 10

state 1 example of mechanical waves

Answer 10

sound waves

Question 11

what is a mechanical wave?

Answer 11

a wave that needs medium or matter to travel through

Question 12

do electromagnetic waves require medium/matter to travel through?

Answer 12

no they do not, can travel through vacuum

Question 13

state an example of longitudinal waves

Answer 13

sound waves

Question 14

describe the way transverse waves travel

Answer 14

• direction of vibration is perpendicular to the direction of travel of the wave

Question 15

describe one way to model waves

Answer 15

• ripples on water
  TRANSVERSE WAVE
  (surface of water moves up and down, waves travel, water does not) - showed by cork

Question 16

does air move when sound waves move?

Answer 16

no - sound is transferred through vibrating molecules, which stay where they are and vibrate about a fixed point

Question 17

what does a time trace diagram do?

Answer 17

• shows how displacement of a wave varies with time

- let us to measure the time period from any point on a wave to point in next

Question 18

what is the equation to find out the time period?

Answer 18

1
———
frequency

Question 19

what is the x-axis label on a snapshot diagram?

Answer 19

distance travelled

Question 20

what is the x-axis label on a time trace diagram?

Answer 20

time (in seconds)

Question 21

what is the formula for wave speed?

Answer 21

s = f x w

Question 22

what is the equation to measure wave speed?

Answer 22

Wavelength (m) x Frequency (hz)

Question 23

difference between transverse and longitudinal waves (vibration of particles in terms of direction of travel)

Answer 23

• transverse = vibrations at right angles of direction of travel
• longitudinal = vibrations at same direction to direction of travel

Question 24

considering what kind of wave light travels as, is it a mechanical wave?

Answer 24

light travels as an electromagnetic wave

- so no, it is not a mechanical wave as it can travel without a medium (CAN TRAVEL IN A VACUUM)

Question 25

why can longitudinal waves pass through faster in a solid compared to a gas?

Answer 25

as particles are very close together, so vibrations can be passed on very fast (faster wave speed)

Question 26

how is the amplitude related to the amount of energy a wave carries?

Answer 26

bigger amplitude = more energy the wave carries

Question 27

how are frequency and wavelength connected?

Answer 27

bigger wavelength = smaller frequency

Question 28

what is the equivilant to peaks and troughs in a longitudinal wave?

Answer 28

compressions (peaks)

rarefractions (troughs)

Question 29

how are ripples on water surfaces used to model transverse waves

Answer 29

• if cork placed on the surface, it is not carried by the wave (only moves up and down)
• ripples travel perpendicular to energy transfer

Question 30

how can the speed of a transverse wave be measured using a ripple tank

Answer 30

1) light shone through tank
2) dark + light patches appear underneath it as light passes through crests + troughs
3) count number of times a dark patch passes through a point in a minute, divide by 60 = frequency
4) measure wavelength by the distance between each dark patch between waves
5) then use v = f x w to calculate speed

alternatively, to reduce systematic errors:
It can be difficult to identify the wavefronts while they are moving
Use a stroboscope (flashing light) matched to the same frequency of the waves, this will be indicated by the waves appearing to be stationary
The frequency can be read from the frequency setting of the stroboscope, and the wavelength will be easier to determine while the waves appear still