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as physics module 4 > 4.4 waves > Flashcards

4.4 waves Flashcards

1
Q

coherence

A

two waves with a constant phase relationship

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2
Q

amplitude

A

the maximum displacement of a wave from its rest position,

metres (m).

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3
Q

displacement (wave)

A

the distance moved by a particle from its rest position

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4
Q

electromagnetic wave

A

a self- spreading transverse wave that does not require a medium to travel through

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5
Q

first harmonic

A

in the fundamental mode of vibration, the length of the string is half the wavelength.

this produces the lowest possible frequency called the first harmonic

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6
Q

frequency, f

A

the number of oscillations passing a point per second

1/period

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7
Q

fundamental frequency

A

the lowest frequency in a harmonic series where a stationary wave forms

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8
Q

progressive wave

A

waves that transfers energy away from a source

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9
Q

longitudinal wave

A

vibrations are parallel to the direction of energy transfer

have the direction of oscillation of particles parallel to the direction of the wave.

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10
Q

transverse wave

A

vibrations are perpendicular to the direction of energy transfer

have the direction of oscillation of particles perpendicular to the direction of travel of the wave.

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11
Q

wavelength

A

the distance between two identical points on consecutive waves

(metres,m)

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12
Q

period

A

the time taken by the wave to complete one full oscillation

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13
Q

coherent sources

A

two waves have a constant phase difference

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14
Q

What do all EM waves have in common?

A

travel through a vacuum

possess both a magnetic wave and an electrical wave interlocked and at right angles to each other

travel at the speed of light

transverse waves

reflected, refracted and diffracted

demonstrate interference

be polarised

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15
Q

plane-polarised wave

A

oscillations of the field and the direction of travel are confined to a single plane

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16
Q

polarising filter

A

produces plane-polarised light by selective absorption of one component of the incident oscillations-

the filter transmits only the component of light polarised perpendicular to that direction

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17
Q

speed of a wave

A

frequency x wavelength

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18
Q

phase

A

a measure of how far through an oscillation a point is

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19
Q

phase difference

A

the proportion of a cycle by which two waves are out of synch

(radians)

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20
Q

wave speed

A

the rate at which a wave spreads through a medium
speed= wavelength/time perio
speed= frequency x wavelength

21
Q

frequency formula

A

frequency = 1/period

22
Q

wave speed formulas

A

wave speed = wavelength/period

wave speed= wavelength x frequency

23
Q

reflection

A

angle of incidence= angle of refraction

when a wave rebounds from a barrier, changing direction but remaining in the same medium

24
Q

refraction

A

the changing of direction of a wave as it enters a different medium due to a change in speed.

The light enters glass from air, the speed decreases which causes the direction to change.

25
Q

diffraction

A

the spreading out of a wave when a it passes a gap or obstacle

occurs when the wavelength about the same size as the gap
As a wave passes a gap, the wave will spread outwards.

If there is a small gap, a more rounder wave is produced. (This is due to less point sources interfering).

26
Q

radio waves

A

10^6 to 10^1

communication

27
Q

Microwaves

A

10^-1 to 10^-3

Communication, cooking

28
Q

Infrared

A

10^-3 to 700nm

Remotes, thermal imaging, heaters

29
Q

Visible light

A

700nm to 400nm

Sight

30
Q

Ultraviolet

A

400nm to 10^-8

Sun tanning, counterfeit detection

31
Q

X-rays

A

10^-8 to 10^-13

Security, bone imaging

32
Q

Gamma rays

A

10^-10 to 10^-16

Sterilisation, cancer treatment

33
Q

common electromagnetic feature

A

All electromagnetic waves travel at c (speed of light), 3×10^8 ms^-1 through a vacuum.

34
Q

differences and similarities between different regions of the electromagnetic spectrum

A

All travel at c (speed of light) through a vacuum

All consist of electric fields perpendicular to magnetic fields

All can be described as photons

They have different frequencies

They have different wavelengths

35
Q

characteristics and dangers of UV-A, UV-B and UV-C radiations

A

UV-A has the longest wavelength of the UV region. The photons carry the least energy so pose the least danger, over exposure can lead to sunburns

UV-B has photons with higher energies which pose a higher risk and can cause skin cancer.

UV-C has the shortest wavelength and highest energy. However, the Ozone layer in the atmosphere prevents UV-C from penetrating.

36
Q

role of sunscreen

A

used to absorb or reflect the UV radiation to prevent the radiation reaching the skin

37
Q

stationary wave

A

formed whenever two progressive waves of same amplitude and wavelength travel in opposite directions and superimpose

38
Q

difference between progressive and stationary waves

A

Progressive waves carry energy from one point to another

whereas a stationary wave is where this energy is stored within the wave rather than transmitted.

39
Q

difference between progressive and stationary waves

A

Both progressive waves and stationary waves cause a displacement in the medium

40
Q

Nodes

A

points on a stationary wave where there is no displacement of the particles at any time.

41
Q

Antinodes

A

points on a stationary wave where there is maximum displacement at any time for the particles.

42
Q

The distance between two adjacent nodes

A

λ/2

43
Q

The distance between an adjacent node and antinode

A

λ/4

44
Q

Fundamental mode of vibration

A

The lowest frequency in a harmonic series where the stationary wave forms.

45
Q

Harmonics

A

Integer number of the fundamental frequency of a stationary wave.

46
Q

total internal reflection

A

when light travels from a material of a higher refractive index to one of a lower refractive index

both refraction and a weak reflected ray occur

47
Q

superposition

A

when two or more waves of the same type meet,

the resultant wave can be found by adding the displacements of the individual waves

they will overlap and interfere

48
Q

constructive interference

A

when waves meet in phase

49
Q

destructive interference

A

when waves arrive at a point completely out of phase

as physics module 4 (5 decks)

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