Unit 3 Flashcards

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1
Q

wave speed formula

A

frequency x wavelength

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2
Q

features of transverse waves

A

has peaks and troughs
vibrations are at right angles ot the direction of propogation

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3
Q

features of longitudinal waves

A

consists of compressions and rarefactions
vibrations are parallel to the direction of propogation

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4
Q

what is a wavefront

A

a surface containing points affected in the same way by a wave at a given time

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5
Q

what is reflection

A

when a wave bounces off a boundary

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6
Q

what is refraction

A

a wave moves from one medium to the other

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7
Q

what is diffraction

A

a wave spreads as it moves through a gap

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8
Q

what happens when a wave moves through a new medium

A

speed and wavelength will change

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9
Q

what happens when a wave passes through a gap

A

wave spreads outwards from the gap in a curved pattern

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10
Q

what images do all mirrors create and what features do they possess

A

virtual images
they are the same size and distance from the mirror
upright

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11
Q

what is a virtual image

A

image that cant be displayed on screens

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12
Q

what is a real image

A

can be projected onto a screen because light actually passes through

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13
Q

what happens when light moves to a denser medium(air to glass)

A

light will slow down and change direction towards the normal

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14
Q

what happens when light moves to a rarer medium(glass to air)

A

it will speed up and move away from the normal

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15
Q

what happens when light enters at the normal

A

there is a change in speed but not change in direction

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16
Q

what is refractive index and how is it calculated

A

measures how much the speed of light changes when it moves from a vacuum to a material
speed of light in vacuum/speed of light in medium = refractive index

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17
Q

what is snells law

A

sin i / sin r = refractive index

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18
Q

What happens when the angle of incidence is larger than the critical angle

A

Total Internal Reflection
light gets reflected back into the medium
only happens in denser to rarer

19
Q

what is the critical angle and how is it found

A

the largest angle of incidence where light can escape the medium
n(refractive index) = 1/sinC

20
Q

What is a converging lens

A

when light rays are brought towards the principle focus

21
Q

what is a diverging lens

A

when light rays are spread out as if coming from the principle focus

22
Q

What is the focal length

A

the distance between the centre of the lens and the principle focus

23
Q

when are virtual images created

A

created when the object is inside the focal length and rays move backwards so the image cannot be created on a screen

24
Q

when are real images created

A

when the object is outside the focal length
image created will be upside down and real

25
Q

what can short sightedness be fixed with

A

by using a diverging lens

26
Q

what can long sightedness be fixed with

A

by using a converging lens

27
Q

why does a beam of white light disperse

A

because different colors travel at different speeds

28
Q

what is light that only contains one frequency called

A

monochromatic light

29
Q

order of colors in decreasing frequency

A

violet,indigo,blue,green,yellow,orange,red

30
Q

what type of waves is the electromagnetic spectrum

A

transverse waves that do not require a medium

31
Q

what speed do electromagnetic waves travel at

A

3 x 10^8 m/s

32
Q

order of the spectrum in increasing frequency

A

radio waves,micro waves,infra red, ultraviolet, x-rays,gamma rays

33
Q

what are radio waves used for

A

transmit television and radio signals

34
Q

what are microwaves used for

A

similar to radio waves
able to penetrate the upper atmosphere
danger is heating effect

35
Q

what is infra red used for

A

can be used for optic fibres
can be used for remote controls
can cause burns

36
Q

what is visible light

A

just electromagnetic radiation that is visible

37
Q

what is ultraviolet radiation used for

A

produced by sun
high amounts of UV can sterilise water and check for fake banknotes
can cause skin cancer and eye conditions

38
Q

what are x rays

A

short wavelength rays
it can pass through materials easily but get absorbed by others
they can damage cells

39
Q

what are gamma rays

A

they can kill cancer cells
can kill living cells and damage DNA
sterilise equipments

40
Q

what type of waves is sound waves

A

they are longitudinal and made of compressions and rarefactions

41
Q

do sound waves require medium

A

yes

42
Q

what range can human ears hear

A

20 to 20,000 Hz

43
Q

what are sounds above 20,000 Hz called

A

Ultrasound

44
Q

what is an echo

A

when sound waves reflect when they encounter a boundary