physics - waves in communcication

Question 1

what are transverse waves?

Answer 1

waves that oscillate perpendicular to the direction of the wave

Question 2

what are longitudinal waves?

Answer 2

waves that oscillate parallel to the direction of the wave

Question 3

what is an example of a transverse wave?

Answer 3

radio waves

Question 4

what is an example of a longitudinal wave?

Answer 4

sound waves

Question 5

what is the wave speed equation?

Answer 5

wave speed = frequency X wavelength

Question 6

what is the measurement for wave speed?

Answer 6

m/s

Question 7

what is the measurement for frequency?

Answer 7

Hz

Question 8

what is the measurement for wavelength?

Answer 8

m

Question 9

what is amplitude?

Answer 9

the distance from the centre line to the top of the crest

Question 10

what is displacement?

Answer 10

the distance moved in a straight line from the starting point

Question 11

what is frequency?

Answer 11

the number of waves that pass a point every second

Question 12

what are oscillations?

Answer 12

repetitive forwards and backwards movement

Question 13

what is a wave?

Answer 13

the transfer of energy without the transfer of matter

Question 14

what is the period of a wave?

Answer 14

the time for a wave make one complete vibrational cycle

Question 15

what is the velocity of a wave?

Answer 15

the direction of propagation

Question 16

what are coherent waves?

Answer 16

waves in phase that have the same frequency

Question 17

what happens during constructive interference?

Answer 17

waves in phase (going up and down) that add to form a bigger amplitude

Question 18

what happens during destructive interference?

Answer 18

waves in antiphase combine to cancel out and add to give zero amplitude

Question 19

what is a wavelength of a wave?

Answer 19

the distance between two points on a wave that have the same amplitude and are moving in the same direction

Question 20

what is the normal?

Answer 20

a line at 90° to the surface at the point the ray crosses between materials

Question 21

what is resonance?

Answer 21

the storing of energy (that comes from an external source) in an oscillation at a stationary wave

Question 22

what is a resonator?

Answer 22

a musical instrumental that stores energy from waves by reflecting wave energy back on itself to form a stationary wave

Question 23

how is resonance produced on stringed instruments?

Answer 23

vibrations of stretched string produce musical notes increasing/decreasing the tension thickness/tension of the string so the length produces stringed notes

Question 24

what is the separation between two adjacent (anti)nodes?

Answer 24

half of a wavelength

Question 25

what happens when a light ray travels from air to glass/plastic?

Answer 25

the speed of light becomes slower and refracts towards the normal

Question 26

how can the frequency of a sound wave be changed in an instrument?

Answer 26

• applying more or less force to an instrument
• using a bigger/smaller instrument

Question 27

what are 3 methods to send and recieve broadband signals?

Answer 27

• satellites
• optical fibres
• cables

Question 28

what is multiplexing?

Answer 28

when broadband sends many signals at the same time

Question 29

what happens when a light ray travels from air to glass/plastic?

Answer 29

the angle of refraction is less than the angle of incidence

Question 30

what happens when a light ray travels from plastic/glass to air?

Answer 30

the angle of refraction is greater than the angle of incidence

Question 31

what is a node?

Answer 31

the points where the amplitude is equal to 0

Question 32

what is an anti node?

Answer 32

the points where the amplitude is the greatest (crest)

Question 33

how can resonance be useful?

Answer 33

• they are useful for musical instruments
• water molecules resonate in microwave ovens
• tv ariels use resonance to get a stronger signal

Question 34

how can resonance be a problem?

Answer 34

• wind may make buildings oscillate dangerously
• skyscrapers may oscillate due to earthquakes
• when machinery resonates it may break

Question 35

what is a phase difference?

Answer 35

the amount by which one wave leads or falls behind another wave

Question 36

what is a stationary wave?

Answer 36

a special type of wave produced when the reflection of transverse waves interfere with each other

Question 37

what is a digital signal?

Answer 37

• a signal made up of binary digits or bits
• each bit is either a 1 or 0
• only has 1 amplitude

Question 38

what is an analogue signal?

Answer 38

• a signal containing lots of different frequencies
• has a varying amplitude

Question 39

what are examples of analogue signals?

Answer 39

• FM radios
• the electrical signal that goes to a loud speaker
• the sound the loudspeaker produces

Question 40

what are examples of digital signals?

Answer 40

• the internet
• bluetooth
• WIFI

Question 41

what happens to the signal inside the ADC?

Answer 41

many times a second the ADC looks at the value of the single and converts it into a binary code

Question 42

what are the two factors that affect the quality of a signal?

Answer 42

1) the sampling rate (how many samples are taken every second

2) the sampling sensitivity (how close together the samples are/how accurate the sampling will be)