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Physics > P6-waves > Flashcards

P6-waves Flashcards

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1
Q

what is the direction of the oscillations in transverse waves?

A

they are perpendicular to the direction of energy transfer

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2
Q

give three examples of transverse waves:

A

light waves, ripples in water, a wave on a string ( like on a guitar)

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3
Q

what direction are the oscillations of a longitudinal wave?

A

they are parallel to the direction of energy transfer

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4
Q

give two examples of longitudinal waves:

A 
sound waves in air
shock waves (e.g seismic waves)
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5
Q

how do waves transfer energy?

A

When waves travel through a medium,the particles of the medium oscillate, transferring energy between each other. (particles stay in the same place though)

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6
Q

what is the amplitude of a wave?

A

the max. displacement of a point on the wave from it’s undisturbed position.

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7
Q

what is the wavelength of a wave?

A

the distance between the same point on two adjacent waves.

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8
Q

what is the frequency of a wave?

A

the number of complete waves passing a certain point per second. measured in Hz

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9
Q

what is 1Hz equal to?

A

1 wave per second

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10
Q

what is the equation linking frequency, wave speed and wavelength?

A

wave speed (m/s)= frequency (Hz) x wavelength (m)

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11
Q

when are waves refracted?

A

when a wave crosses a boundary at an angle, it’s direction gets changed.

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12
Q

what determines how much a wave is refracted?

A

How much the wave speeds up/slows down . This depends on the density of the material

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13
Q

what happens to a wave that slows down when it crosses the boundary?

A

It bends towards the normal.

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14
Q

what happens to a wave that speeds up as it crosses a boundary?

A

it bends away from the normal

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15
Q

what changes and what stays the same when a wave is refracted?

A

the wavelength changes, the frequency stays the same.

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16
Q

what is the optical density of a material?

A

a measure of how quickly light can travel through it. Higher optical density-light waves travel slower.

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17
Q

Drawing a ray diagram for refraction:
draw in the __________between 2 materials, and the _______
draw an _____ ray which meets the normal at the boundary. the < between the ray and the normal is the angle of _________.
now draw the ________ray . the angle of refraction depends on the _______ of the material.

A

boundary, normal. Incident, incidence.refracted, optically dense.

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18
Q

radio waves are apart of…?

A

the electromagnetic spectrum. EM waves are made up of oscillating electric and magnetic fields.

19
Q

radio waves travel at the speed of what?

A

light

20
Q

are radio waves transverse or longitudinal?

A

transverse.

21
Q

can radio waves travel through a vacuum?

A

yes

22
Q

give three examples of signals that radio waves carry:

A

Tv, radio and mobile phone signals

23
Q

give another use of radio waves:

A

they can wirelessly connect a computer to a printer. Bluetooth

24
Q

State three properties of short length radio waves:

A

they carry more information
they have a shorter range
they spread out less ( they don’t weaken as much)

25
Q

what are radio wave lengths of less than 1 metre used for and why?

A

they are used for TV broadcasting from TV masts. This is because they carry a lot of information.

26
Q

what are radio waves of length 1m-100m used for and why?

A

local radio stations, emergency services. they have a short range.

27
Q

what are radio waves length greater than 100 m used for?

A

national/international radio stations. They have a longer range.

28
Q

what is different about how long length radio waves compared to short ones?

A

Long waves diffract around the curved surface of the earth.They can diffract around hills and into tunnels. Whereas short wavelengths are reflected from the ionosphere

29
Q

transmitting and receiving radio waves:
1-microphone produces an_______ ______
2-this causes_____to oscillate in _______ aerial
3-the aerial emits ______ waves
4-the waves are absorbed by ______ aerial
5- electrons_____ in the receiver, generating an _______ current with the same _______ as radio waves.

A 
alternating current
electrons, transmitter
radio
receiver
oscillate, alternating
frequency
30
Q

if you can’t hear radio waves, how can radios produce the noise from the waves?

A

radio waves carry signals which the receiver converts into sound waves.

31
Q

How do lenses work?

A

they refract light and change it’s direction.

32
Q

what are the two types of lens?

A

concave and convex.

33
Q

what is the shape of a convex lens and how does it refract light?

A

It bulges outwards () . Rays of light parallel to the axis are brought together and converge at the principal focus.

34
Q

what is the shape of a concave lens and how does it refract light?

A

it caves inwards )(. rays of light parallel to the axis diverge.

35
Q

what is the axis of a lens?

A

a line passing through the middle of the lens

36
Q

what is the principal focus of a convex lens?

A

where the rays hitting the lens parallel to the axis all meet.

37
Q

what is the principal focus of a concave lens?

A

where all the rays hitting the lens parallel to the axis APPEAR to all come from (they can be traced back until they all appear to meet up at a point behind the lens)

38
Q

what is the focal length?

A

the distance from the centre of the lens to the principal focus (there’s a principal focus on either side of the lens)

39
Q

what are the three rules of convex lenses?

A

1-an incident ray parallel to the axis refracts through the lens and passes through the principal focus on the other side
2-an Incident ray passing through the principal focus will refract through the lens and travel parallel to the axis
3-an incident ray traveling through the centre of of the lens carried on in the same direction.

40
Q

what are the three rules for concave lenses?

A

1-An incident ray parallel to the axis will refract through lens and travel in line with the principal focus
2-an incident ray travelling through lens towards principal focus will refract and travel parallel to the axis
3-incident ray passing through centre carries on in same direction

41
Q

what is a real image and give an example:

A

the light from an object comes together to form an ‘image on a screen’. Eg the image formed on an eye’s retina.

42
Q

what is a virtual image? give an example

A

where rays are diverging so light appears to be coming from somewhere else. Eg a mirror. you can use a magnifying glass to get a virtual image.

43
Q

what three things are needed to describe an image?

A

1-size compared to object
2-if it’s upright or inverted compared to object
3-of its real or virtual

44
Q

will a concave lens always give a real or virtual image?

A

virtual

Physics (4 decks)

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