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Physics > 3. Waves > Flashcards

3. Waves Flashcards

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0
Q

What is wavefront

A

The peak of a transverse wave

The compression of a longitudinal wave

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1
Q

What is speed of wave

A

Distance travelled by a wave peak or trough every second

Unit m/s

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2
Q

What is frequency

A

The number of complete waves passing a point in one second

Unit hertz

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3
Q

What is wavelength

A

Distance from 1 wave peak to another

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4
Q

What is amplitude

A

The distance from the middle to the peak or the trough

The bigger the amplitude, the more energy it carries

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5
Q

How to calculate speed of wave

A

Wavelength x frequency

Unit m/s

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6
Q

Describe transverse wave

A

Vibrations are perpendicular to the direction in which the waves are traveling

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7
Q

Describe longitudinal waves

A

Vibrations are parallel to the direction in which the waves are traveling

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8
Q

Describe refraction when waves slow down

A

When water waves pass through shallow water
Wavefront crowded together so wavelength gets smaller
Waves slow down when pass from a less to a more dense material
When a wave is slowed down, it is refracted toward the normal
I>r

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9
Q

Describe refraction when a wave speed up

A

Wavefront spread out -> wavelengths gets larger
Move from a denser to a less dense material
It is refracted away from the normal
I

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10
Q

Describe diffraction

A

It is the spreading of waves when they pass through a gap or move past an obstacle
Narrower the gap, the more waves spread out and vice versa
Wavelength does not change on diffraction
For noticeable diffraction, the gap must be similar size to wavelength

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11
Q

Describe the image given by reflection

A

As far behind the mirror as the object is in the front
Same size as object
Laterally inverted ( left and right are swap around)
The image is virtual, cannot be focused on a screen

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12
Q

What is the law of reflection

A

Angle of incidence = angle of reflection

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13
Q

Describe the angle of refraction and incidence when light refract

A

Travel from less dense -> more dense
I > r
Travel from a more dense -> less dense
R> I

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14
Q

What is critical angle

A

The angle at which the refracted ray emerges along the boundary

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15
Q

What happen if i > or

A

I > critical angle -> the light ray is totally internally reflected
I refraction

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16
Q

How to calculate the refractive index

A

Speed of light in air / speed of light in medium

Sin I / sin r

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17
Q

Define refractive index

A

A measure of the change of direction of a light ray at non-normal incidence when it passes from air into the substance

18
Q

What is the law of refraction

A

Refractive index = sin I / sin R

19
Q

What is the principal focus

A

The point where parallel Ray directed straight at the converging lens are focused

20
Q

What is the focal length

A

The distance from the lens to the principal focus

21
Q

How does converging lens work

A

By changing the direction of light passing through it

22
Q

When is a real and inverted image formed if light is directed through a converging lens

A

If the object is further from the lens than the principal focus is

23
Q

When is the image real and diminish

A

When object is beyond 2F

Image is between F and the lens

24
Q

When is an object real and same size

A

The object is at 2F

Image at 2F on the other side

25
Q

When is an object real and magnified

A

The object is between F and 2F

The image is beyond 2

26
Q

What happen if the object is between F and the lens

A

The image will be virtual upright, magnified and on the same side as the object

27
Q

Describe the dispersion of light

A

White light has all the colors of the visible spectrum in it
Each color light is refracted differently bc the speed of light in glass depend on its color
The result is that the beam of white light is split into separated color by the prism

28
Q

Describe the main feature of the electromagnetic spectrum

A

Can travel in high speed through a vacuum
Travel at the speed of light 3x10^8
Can transfer energy
They are transverse wave
When a wave hits an object, the energy it carries is transferred to the object as ke

29
Q

What is monochromatic

A

Light of a single wavelength and color

30
Q

The uses of radio wave

A

Radio and television communication

31
Q

The use of microwaves

A

Satellite television and telephone

To heat food

32
Q

Uses of infra red

A

Electrical appliance, remote control for television and intruder alarm

33
Q

Use of x Ray

A

Medicine - kill cancer cell and security

34
Q

Describe the danger issue of x Ray

A

Cause cancer, mutation bc they they are ionizing - they create ions I substance they pass through

35
Q

Describe the danger of microwaves

A

Penetrate into the body and have a heating effect on body tissue
Damage skin tissue and internal organs as it cause internal heating

36
Q

What is the source of sound

A

Any object vibrating in air creates sound waves

Sound wave in air consists of alternate compression and rarefaction passing though the air

37
Q

Describe the motion of sound waves

A

When it pass through air,the air molecules in the path move forward, causing compression, and backward, causing rarefaction, along the direction in which the waves are moving

38
Q

What is the frequency in which human can hear

A

20hz -> 20 000 hz

39
Q

Describe the speed of sound

A

Medium is needed to transmit sound waves
Speed : solid > liquid > gas
340 - 1400 - 4000

40
Q

What does frequency and amplitude represent

A 
Frequency = pitch, height frequency -> high pitch
Amplitude = loudness, high amplitude -> loud
41
Q

Describe echo

A

It is the reflection of sound

Sound waves reflecting off the wall and return to you

42
Q

How to eliminate echo

A

Cover wall in soft fabric which absorbs sound wave

Make the wall surface uneven or not smooth so reflected sound waves are scattered

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