1) Waves

Question 1

what do waves do?

Answer 1

transfer energy and information without transferring matter

Question 2

what happens with water and sound waves when travelling?

Answer 2

• wave travelling not sound/water

- eg if you drop a twig on water ripples come out but ripples don’t carry the twig or water

Question 3

what is the frequency of waves?

Answer 3

• number of waves passing a a point per second

- Hz

Question 4

what is wavelength?

Answer 4

• length of a full cycle of wave

- from one point to the same point on the next

Question 5

what is wave amplitude?

Answer 5

-displacement from rest position to crest

centre to top of single wave

Question 6

what is a wave period?

Answer 6

• number of seconds for one full cycle

- period= 1 / frequency

Question 7

what are transverse waves?

Answer 7

• perpendicular waves (sideways)
• all electromagnetic waves
• S-waves (a seismic wave)
• ripples

Question 8

what are longitudinal waves?

Answer 8

• parallel to direct waves
• sound waves, P-waves (a seismic wave)
• squash up and stretch out

Question 9

what are 2 equations to work out wave speed?

Answer 9

V= D / t 
V= F X wavelengths (m)

V= wave speed m/s
t= time (s)

Question 10

how can you measure velocity of sound in air?

Answer 10

• set up oscilloscope with 2 microphones
• set with microphones together then move slowly away
• until waves on oscilloscope are equal
• mesure distance of microphones
• use V= F X wavelength

Question 11

how can you measure velocity of ripples on water surfaces?

Answer 11

• use signal generator to make ripples
• use strobe light to make shadows
• alter generater into waves look still
• distance between wave= wavelength
• use V= F X wavelength

Question 12

what happens when a wave is reflected?

Answer 12

• ‘sent back’ away from second material

- how echos are created

Question 13

what happens when a wave is transmitted?

Answer 13

• second material
• carries on through new material
• used in communications, glass, lenses

Question 14

what happens when a wave is absorbed?

Answer 14

• second material
• wave transferred energy into materials energy stores
• often thermal energy

Question 15

what happens when a wave is refracted?

Answer 15

-wave changing directions at boundary

Question 16

what is the process of a wave being refracted?

Answer 16

• waves different speeds in materials with different densities
• it boundary at angle, change direction
• greater change in speed, goes more bent

Question 17

what do different materials do with varying wavelengths?

Answer 17

-absorb, transmit, refract and reflect I different ways

Question 18

why does a ray diagram show?

Answer 18

the path that a wave travels

Question 19

what is the normal on a ray diagram?

Answer 19

• line down middle

- boundary

Question 20

what is the angle of incidence on a ray diagram?

Answer 20

-angle between normal and incoming ray

Question 21

what is the angle of refraction?

Answer 21

-angle between normal and refracted ray

Question 22

what is the method to investigate sound waves as vibrations in solids?

Answer 22

1.measure+record length of metal rod
2.set up clamps, hammer, microphone to computer
3. tap rod with hammer
4. record peak frequency
5. repeat to get average
6. calculate speed v=f X wavelength
wavelength= twice length of rod

Question 23

what is the frequency of ultrasound?

Answer 23

above 20,000Hz

or 20KHz

Question 24

what sound frequencies can the human ear hear?

Answer 24

20Hz to 20,000Hz

Question 25

what are the uses of ultrasound?

Answer 25

• checking unborn babies

- sonar, on ships to detect fish

Question 26

what are the uses of infrasound?

Answer 26

• elephants to communicate over long distances

- detect volcanic eruptions, volcanos release infrasound