physics - waves in communcication Flashcards

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1
Q

what are transverse waves?

A

waves that oscillate perpendicular to the direction of the wave

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2
Q

what are longitudinal waves?

A

waves that oscillate parallel to the direction of the wave

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3
Q

what is an example of a transverse wave?

A

radio waves

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4
Q

what is an example of a longitudinal wave?

A

sound waves

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5
Q

what is the wave speed equation?

A

wave speed = frequency X wavelength

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6
Q

what is the measurement for wave speed?

A

m/s

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7
Q

what is the measurement for frequency?

A

Hz

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8
Q

what is the measurement for wavelength?

A

m

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9
Q

what is amplitude?

A

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

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10
Q

what is displacement?

A

the distance moved in a straight line from the starting point

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11
Q

what is frequency?

A

the number of waves that pass a point every second

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12
Q

what are oscillations?

A

repetitive forwards and backwards movement

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13
Q

what is a wave?

A

the transfer of energy without the transfer of matter

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14
Q

what is the period of a wave?

A

the time for a wave make one complete vibrational cycle

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15
Q

what is the velocity of a wave?

A

the direction of propagation

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16
Q

what are coherent waves?

A

waves in phase that have the same frequency

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17
Q

what happens during constructive interference?

A

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

18
Q

what happens during destructive interference?

A

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

19
Q

what is a wavelength of a wave?

A

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

20
Q

what is the normal?

A

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

21
Q

what is resonance?

A

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

22
Q

what is a resonator?

A

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

23
Q

how is resonance produced on stringed instruments?

A

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

24
Q

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

A

half of a wavelength

25
Q

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

A

the speed of light becomes slower and refracts towards the normal

26
Q

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

A
  • applying more or less force to an instrument
  • using a bigger/smaller instrument
27
Q

what are 3 methods to send and recieve broadband signals?

A
  • satellites
  • optical fibres
  • cables
28
Q

what is multiplexing?

A

when broadband sends many signals at the same time

29
Q

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

A

the angle of refraction is less than the angle of incidence

30
Q

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

A

the angle of refraction is greater than the angle of incidence

31
Q

what is a node?

A

the points where the amplitude is equal to 0

32
Q

what is an anti node?

A

the points where the amplitude is the greatest (crest)

33
Q

how can resonance be useful?

A
  • they are useful for musical instruments
  • water molecules resonate in microwave ovens
  • tv ariels use resonance to get a stronger signal
34
Q

how can resonance be a problem?

A
  • wind may make buildings oscillate dangerously
  • skyscrapers may oscillate due to earthquakes
  • when machinery resonates it may break
35
Q

what is a phase difference?

A

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

36
Q

what is a stationary wave?

A

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

37
Q

what is a digital signal?

A
  • a signal made up of binary digits or bits
  • each bit is either a 1 or 0
  • only has 1 amplitude
38
Q

what is an analogue signal?

A
  • a signal containing lots of different frequencies
  • has a varying amplitude
39
Q

what are examples of analogue signals?

A
  • FM radios
  • the electrical signal that goes to a loud speaker
  • the sound the loudspeaker produces
40
Q

what are examples of digital signals?

A
  • the internet
  • bluetooth
  • WIFI
41
Q

what happens to the signal inside the ADC?

A

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

42
Q

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

A

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)