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AS Physics > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

What is a wave?

A
  • A periodic disturbance and is continuous

- Something that has travelled away from equilibrium position

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2
Q

How would you classify a mechanical wave?

A

Some physical material is being disturbed

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3
Q

Give some examples of mechanical waves

A

Sound waves within water or air, seismic waves

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4
Q

How would you classify an electromagnetic wave?

A

Disturbance in electric or magnetic fields. No matter or particles are required.

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5
Q

Which of mechanical and electromagnetic waves can travel through a vacuum?

A

Electromagnetic

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6
Q

Give examples of electromagnetic waves

A

Radio, microwave, infrared, visible, ultraviolet, x-ray, gamma rays

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7
Q

How would you classify a transverse wave?

A

A disturbance which creates the wave. Oscillations are moving perpendicular to the direction of energy transfer

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8
Q

How would you classify a longitudinal wave?

A

The disturbance creates the wave. Oscillations are moving parallel to the direction of energy transfer

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9
Q

What are compressions in a wave?

A

Where the particles in a wave are closer together

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10
Q

What are rarefractions in a wave?

A

Where the particles in a wave are further apart

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11
Q

With compressions are rarefractions, which has a higher pressure?

A
  • Compressions have a higher pressure

- Rarefractions have a lower pressure

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12
Q

Which type of waves can be polarised?

A

Transverse waves

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13
Q

How does polarisation work?

A

A transverse wave passes through a polaroid, and the polaroid only allows displacement from equilibrium in one direction, and the plane is defined

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14
Q

What is the direction of displacement like in an unpolarised wave?

A

In all directions

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15
Q

Describe the graph of the intensity of signal against angle of rotation for: The unpolarised ray passing through 2 polaroids, and the 2nd one being rotated

A

0 deg - full intensity
90 deg- no intensity
180 deg - full intensity
270 deg - no intensity

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16
Q

On a graph, what is the difference between time period and frequency?

A

Time period is the duration of one cycle

Frequency is the number of cycles in one second

17
Q

What is a radian?

A

Unit for measuring an angle

18
Q

What is the unit for radians?

A

It has none, it is a ratio

19
Q

How many pi radians are in 360 degrees?

A

2 pi

20
Q

What are the 2 situations that you would deal with phase difference?

A
  • Looking at the phase difference between 2 points on the same wave
  • Have 2 waves, look at phase difference at the point they meet (interference)
21
Q

How would you measure the phase difference between 2 points on the same wave?

A

Measure lamba, and the distance between 2 points.
d/lamba gives fraction of the wave.
d/l x 2 pi = phase difference in radians
d/l x 360 = phase difference in deg

22
Q

In refraction, from less dense -> more dense mediums, how does speed and wavelength change?

A

Speed and wavelength decrease

23
Q

In refraction, from more dense -> less dense mediums, how does speed and wavelength change?

A

Speed and wavelength increase

24
Q

What are wavefronts?

A

Points in a wave that have the same phase. They are perpendicular to the direction of travel

25
Q

What is superposition?

A

When waves pass through each other, and combine for an instant

26
Q

What does the superposition of waves look like for 2 waves that pass through each other and are in phase?

A

The amplitude and trough doubles - Constructive interference

27
Q

What does the superposition of waves look like for 2 waves that pass through each other and are out fo phase?

A

The amplitudes and troughs cancel out, giving a flat line - Destructive interference

28
Q

What is the path difference of 2 waves?

A

Path difference is the difference between the lengths of two paths.

29
Q

What must be true about the wavelengths for constructive path difference?

A

The difference between paths is a multiple of the wavelength

30
Q

What must be true about the wavelengths for destructive path difference?

A

The difference between paths is not a multiple of the wavelength

31
Q

Define interference

A

Formation of points of cancellation or reinforcement where 2 coherent waves pass through each other

32
Q

When are 2 sources of anything coherent?

A

2 sources of wave are coherent if they emit waves with a constant phase difference

33
Q

What are oscilloscopes?

A

Devices that can measure voltages very accurately

34
Q

What can you measure with a cathode ray oscilloscope?

A

Time period, amplitude and time events

AS Physics (12 decks)

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