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phy > Wave > Flashcards

Wave Flashcards

1
Q

how to calculate the maximum no. of maxima in double slit experiment

A

path difference < slit difference (a)
because of triangle inequality
(length of two sides> other side of triangle)

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2
Q

what can be observed under dispersion

A

A colour spectrum is seen

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3
Q

how to capture image from a convex lens

A

sharp image by using a screen

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4
Q

why its better to calculate the 2nd maxima rather than the 1st one in diffraction grating

A

smaller percentage error

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5
Q

why its not a good choice to use LED in double slit

A

the screen will be uniformly illuminated

light form LED is incoherant

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6
Q

what is the condition when double slit experiment is performed

A

D&raquo_space; a
D» y
Make use of small angle approximation sin veta ~ tan beta

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7
Q

why slit width need to be narrow in double slit

A

to ensure the light through 2 slits diffract enough to interfere

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8
Q

what factors will affect speed of wave

A

tension increases, speed increases

mass increases , speed decreases

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9
Q

fundamental frequency in stationary waves

A

when wavelength= 2L (最盡wavelength時候ge frequency)

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10
Q

what would happen to the antinodal lines if the separation of the sources is reduced slightly

A

the separations of both lines is greater

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11
Q

Compare the brightness of the image with different size

A

As the light energy collected by the lens is the same for both case, an enlarged image has the same amount of light energy distributed over a larger image, so the intensity of light decreases.

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12
Q

why alternate maxima and minima are shown along a plane

A

path difference of the diffracted waves from the slits to probe varies along XY
constructive and destructive interference occur alternately to give maxima and minima

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13
Q

double slit experiment

is central maximum count as a maximum?

A

YES

0 lamda = first maxima

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14
Q

why radio waves of lower frequencies not suitable for use in radar

A

radiowaves with lower frequencies have greater diffraction effect
radio waves not to be reflected from small objects.

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15
Q

放大鏡 english?

A

magnifying glass

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16
Q

how to find focal length with experimental setup

A

place the lens on the paper and trace its outline using ray tracing method such as
direct and trace a light ray parallel to the principle axis

direct another light ray parallel to the principle axis and trace the path of the ray on the paper

Extend the emerging rays and locate the point of intersection

Measure the distance from the point of intersection to the center of the lens which gives the focal length of the lens.

Error: Scale accuracy of the ruler (cor to nearest mm)

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17
Q

why a minimum occurs at a point

A

The waves from A and B are in antiphase at the point and the path difference at the point = (n + 0.5)lamda
So destructive interference occurs to form a minimum

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18
Q

wt is the suitable and normal setting for young double slit experiment
single slit width?
double slit separation?
distance between screen and double slit?

A

1mm
0.1mm
1m

D=10m too long not practical

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19
Q

what is the factor affecting wavespeed

A

medium only!!!!!!!!!!
(different medium causing refraction)
changing frequency only wont affect wavespeed

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20
Q

what is the factor affecting frequency

A

only the change of the source

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21
Q

what is the distinctive properties of wave

A

interference

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22
Q

can ultrasound sterilize drinking water

A

no

thats ultra violet

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23
Q

what is the nature of image formed by convex lens when u > f

A

real and inverted

while inverted means 左右倒轉 上下倒轉

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24
Q

why the slit width has to be very narrow in order for the double slit pattern to be observed

A

To ensure that the light through the 2 slits diffract enough to interfere

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25
Q

converging lens is?

A

convex lens

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26
Q

diverging lens is?

A

concave lens

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27
Q

state the law of reflection

A

The incident ray, reflected ray and the normal all lie in the same plane
the angle of incidence is always equal to the angle of reflection

28
Q

how a regular reflection is formed

A

if the surface is flat and smooth
the normal at different positions are parallel to one another
the parallel rays are reflected in the same direction

29
Q

how a diffuse reflection is formed

A

the normal at different points on a rough surface point at different directions
parallel rays of light are reflected towards different direction

30
Q

what is virtual image

A

an image cannot be projected on screen

31
Q

names in a lens

A

optical centre
principle axis
principle focus
focal length

32
Q

how does travelling wave transmit energy

A

it transmits energy without transferring matter

like a ball on water wont move inward or outward

33
Q

what is a transverse wave

A

a transverse wave is one in which the particle vibrations are perpendicular to the direction of travel of the wave

34
Q

what is a longitudinal wave

A

a longitudinal wave is one in which the particle vibrations are along the direction of travel of the wave

35
Q

what are the points in transverse wave

A

upper point : crest

lower point : trough

36
Q

what are the points in longitudinal wave

A

compression and rarefaction

37
Q

what is amplitude

A

it is the maximum displacement of the particle from its equilibrium position

38
Q

what is wavelength

A

it is the minimum distance over which the waveform repeats itself

39
Q

what is in phase

A

when two particles are sperated by any whole number of wavelength are vibrating in phase in a travelling wave
always move in the same direction

opposite: in anitiphase

40
Q

in a travelling wave

when f increase, then?

A

wavelength decrease

wave speed along a stretched spring is in general independent of the frequency.

41
Q

what does speed of wave usually depends on?

A

the medium it travels through

42
Q

what is wavefront

A

a line of neighbouring points which are vibrating in phase

43
Q

what is diffraction

A

the bending or spreading of waves around the edge into the shadow of the obstacle

44
Q

when will the diffraction of waves at a gap be observable

A

when the width of the gap is comparable to the wavelength of the waves

45
Q

how constructive interference is formed

A

it occurs at position where two waves arrive in phase, Particles at those positions vibrate with a larger amplitude

the path difference is equal to whole numbers of wavelength

46
Q

how destructive interference is formed

A

it occurs at position where two waves arrive in antiphase. Particles at those position remain stationary

the path difference is equal to 0.5 lambda, 1.5 lambda and so on

47
Q

what are antinodal lines

A

where constructive interference occurs

48
Q

what are nodal lines

A

where destructive interference occurs

49
Q

what is a coherant source

A

when two source have the same frequency and a constant phase difference

50
Q

factors affecting the inteference pattern

A

wavelength of the wave
when wavelength decreases, nodal and antinodal lines become more closely spaced.

the separation between the sources
when the separation increases, nodal and antinodal lines become more closely spaced.

51
Q

what is unique about wave

A

only wave exhibit diffraction and interference

52
Q

what are the names in stationary wave

A

nodes
where particles do not vibrate

antinodes
where particles vibrate with the largest amplitude.

53
Q

how a stationary wave is formed

A

it results from the interference of two waves with the same frequency and amplitude traveling at the same speed in opposite direction

54
Q

state the principle of superposition

A

it states that when two waves meet, the displacement of any point on the resultant wave is the sum of the displacements due to both waves at the point

55
Q

how interference is formed

A

when two waves cross

56
Q

where is the energy in stationary wave

A

energy is stored

not transmitting

57
Q

what is monochromatic light

A

light with a single wavelength

58
Q

why the fringe formed by plane transmission grating are brighter

A

a grating allow more light to pass through as it has much more slits than a double slit

59
Q

what will glow under UV radiation?

A

fluorescent

60
Q

what em wave is used in radar

A

microwaves

61
Q

how sound is produced

A

when a sound source vibrates

the air particles nearby are forced to vibrate and in turn set the neighboring air particles in vibration

62
Q

what is mechanical wave

A

different from electromagnetic waves

it need a medium to travel through such as sound wave and water wave

63
Q

what is the unit measuring sound intensity level

A

dB

decibels

64
Q

what is monochromatic

A

the beam only consists of a single frequency

65
Q

what is the function of spongy lining at the edge of the ripple tank

A

prevent water waves from bouncing back at the edges of the tank
to absorb the water waves

66
Q

why cant a transverse wave push a ball to the shore

A

transverse wave transfer energy but not matter

67
Q

what is the name of that mirror on the car

A

rear-view mirror

phy (7 decks)

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