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AS Level Physics SABZ > Chapter 13~waves 🌊 > Flashcards

Chapter 13~waves 🌊 Flashcards

Definitions, key ideas 💡 and formulae

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1
Q

What are waves?

A

Waves are a means of transferring energy ⛮ or “information” from one point to another caused by vibrations. Also referred to as a periodic disturbance travelling through space, characterised by a vibrating medium.

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2
Q

Definition of progressive waves

A

A wave that carries energy ⛮ from one place/posifion to another through a material or vacuum.

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3
Q

Definition of a mechanical wave : and an example

A

°it is a wave that requires a material medium to move through, for example sound 🔊.

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4
Q

Definition of displacement :

A

The distance of a point on the wave 🌊 from its underdisturbed position or equilibrium position

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5
Q

Definition of amplitude, A:

A

The maximum displacement of any point on the wave from its underdisturbed position / equilibrium

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6
Q

A greater amplitude result in what for sound waves?

A

A louder sound 🔊

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7
Q

Definition of wavelength :

A

The distance from any point on a wave to the next exactly similar point, measured in metres. (e.g. From crest to crest)

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8
Q

Definition of period, T:

A

The time take for one complete oscillation of a point in a wave, measured in seconds.

The time taken for one wave /oscillation to pass a point.

The time taken for a particle to complete a full oscillation.

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9
Q

Definition of frequency, f :

A

The number of oscillation per unit time of a point in a wave, measured in hertz (Hz).

The number of waves/oscillations that pass a point per second.

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10
Q

A higher pitch is a result of..

A

A higher frequency

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11
Q

Definition of a longitudinal wave : and an example

A

Waves in which the particles of the medium vibrate parallel to the direction of the wave propagation (motion) or the wave velocity.

Example: sound 🔊

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12
Q

Definition of transverse waves :

Plus an example

A

Waves in which the particles of the medium vibrate at right angles or perpendicular to the wave motion /propagation /velocity.

Example : light wave

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13
Q

Frequency is the reciprocal of?

A

The period (T)

F= 1/T

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14
Q

Definition of compressions 🗜 :

A

A region in a longitudinal wave where the particles are closest together and where the air pressure is greater than its mean value.

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15
Q

Definition of rarefaction :

A

A region in a longitudinal wave where the particles are furthest apart and the air pressure is less than its mean value.

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16
Q

Definition of phase difference:

A

°the difference in the phases of 2 oscillating particles, experienced in degrees or radians. It also refers to the amount by which one wave leads or lags another wave.

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17
Q

How many degrees is equivalent 1 radian?

A

180°

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18
Q

Intensity of a wave 🌊 :

A

The rate of energy ⛮ transmitted per unit area at right angles to the wave velocity.

19
Q

What are the units for intensity?

A

Watts per square metre, Wm-2

20
Q

Formula for intensity

A

Intensity = power /cross-sectional area

21
Q

The intensity of a wave generally decreases as it travels along for 2 reasons :

A
  1. The wave may ‘spread out’

2. The wave may be absorbed or scattered

22
Q

Intensity is proportional to..

A

The square of the amplitude.

23
Q

What is the wave equation and how is it derived in two steps?

A

v = f × ♈

v-velocity
F-frequency
♈-wavelength

Derived from :
Step 1 :
speed =distance / time

v= ♈÷ 1/T

Step 2 : rewrite this

v = ♈ x f

Bec 1/T =f

24
Q

What is the Doppler effect?

A

The change in frequency or wavelength of a wave 🌊 observed when the source of the wave is moving towards or away from the observer (or the observer is moving relative to the source

25
Q

Short meaning of the Doppler effect

A

It is the change in frequency due to the relative motion between the observer and source.

26
Q

Formula for observed frequency =

A

f(o) =[f(s) v] /[v +/- v(s)]

27
Q

When do you use a plus ➕ in the observed frequency formula?

A

This is used when either the observer / source is moving AWAY from the other

28
Q

When do you use a minus ➖ in the observed frequency formula?

A

When there is movement towards of either the observer or source

29
Q

What two things are unaffected by the movement of the source?

A
  1. The frequency f(s) of the source, it still emits f(s) waves per second
  2. The speed v of the waves
30
Q

Definition of electromagnetic spectrum :

A

The family of transverse 🚦 waves 🌊 that travel through a vacuum at a speed of 3.00 × 10^8.
They are a group of waves with common properties

31
Q

The five properties of electromagnetic waves 🌊 :

A
  1. All travel at the speed 🚤 of light 🚦

c= 3 × 10^8

Therefore (c =f ♈)

  1. All can be polarised
  2. All can be reflected, refracted, diffracted and absorbed
  3. All travel through a vacuum
  4. All can undergo interference
32
Q

What are the seven electromagnetic waves? 🌊

In order of decreasing wavelength

A
  1. Radio waves
  2. Microwaves
  3. Infared
  4. visible
  5. Ultra-violet
  6. X-rays
  7. Gamma rays (y-rays)
33
Q

What is the wavelength range in metres of radio 📻 waves?

A

> 10^6 to 10^-1

34
Q

What is the wavelength range in metres of microwaves?

A

10^-1 to 10^-3

35
Q

What is the wavelength range in metres of infared?♥

A

10^-3 to 7×10^-7

36
Q

What is the wavelength range in metres of visible waves?

A

7×10 ^-7(red) to 4× 10^-7 (violet)

37
Q

What is the wavelength range in metres of ultraviolet waves?

A

4 × 10^-7 to 10^-8

38
Q

What is the wavelength range in metres of x-rays? ☠️💀

A

10^-8 to 10^-13

39
Q

What is the wavelength range in metres of x-rays? ☠️💀

A

10^-8 to 10^-13

40
Q

What is the wavelength range in metres of Y-rays ( gamma rays)?

A

10^-10 to 10^-16

41
Q

State all 7 ranges of wavelengths from decreasing wavelengths :

A

R : >10^6 to 10^-1

M: 10^-1 to 10 ^-3

I: 10^-3 to 7 × 10^-7

V: 7 × 10^-7 (red) to 4 ×10 ^-7 (violet)

U: 4× 10 ^-7 to 10 ^-8

X : 10 ^-8 to 10^-13

Y: 10^-10 to 10 ^-16

42
Q

Definition of an electromagnetic wave :

A

A disturbance in the electric and magnetic fields in space

43
Q

What is polarisation?

A

It is the process in which transverse waves are restricted to vibrate in one plane (only)

AS Level Physics SABZ (17 decks)

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