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P5-P8 > p5.3 > Flashcards

p5.3 Flashcards

1
Q

what do you use a ray diagram to show?

A

what happens when electromagnetic waves hit a boundary/travel through matter

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2
Q

what is the law of reflection (and where is it only true)

A

angle of incidence = angle of reflection

  • only true for plane mirrors
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3
Q

when describing an object formed by refraction of a lens, which 3 aspects must you describe?

A
  • whether the object is real/virtual
  • whether the object is inverted/upright
  • whether the object is diminished/magnified
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4
Q

what is a virtual image?

A

image that is formed where light rays appear to come from

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5
Q

what is an upright image?

A

when the image is the same way up as the object

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6
Q

where does specular reflection occur?

A
  • from a smooth surface
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7
Q

what is the difference between specular and diffuse reflection?

A 
specular = occurs from smooth surface 
diffuse = occurs from rough surface
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8
Q

what is the difference between specular and diffuse reflection in terms of the clarity of the image?
(and how is it produced)

A

s = parallel rays reflected in the same direction
CLEAR IMAGE

d = parallel rays SCATTERED in different directions
UNCLEAR IMAGE

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9
Q

what do lenses do?

A

refract light passing through them

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10
Q

define the principal focus?

A

the point where parallel rays meet/appear to meet

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11
Q

what is the focal length?

A

the distance from the lens to the principal focus

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12
Q

define what a convex lens does

A

refracts parallel rays passing through it CONVERGE to a point

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13
Q

give 3 uses of convex lenses

A
  • magnifying glass (object needs to be help closer than focal point so magnified virtual upright image forms)
  • camera forming an image of an object far away (needs to focus, not refract light)
  • correcting long sight
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14
Q

define what a concave lens does

and give one use

A

refracts parallel rays passing through it to DIVERGE

- correcting short sight

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15
Q

difference between rays travelling from nearby objects vs distant objects

A
  • nearby = seem to be diverging from each other (so lens has to be thick to focus to a specific point)
  • distant = seems to be traveling parallel to each other (so lens refracts light a lot less)
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16
Q

what is a real image?

A

image that is formed where light rats meet

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17
Q

what is the difference between virtual and real images (ie. where they focus)

A

virtual = focus on same side as object

real = focus on opposite side as object

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18
Q

what kind of lens are real images made from?

A

converging/convex lens

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19
Q

what kind of lens are virtual images made from?

A

can use both a convex and concave lens

  • only convex = object must be inside focal point
  • concave (always produces virtual image)
20
Q

define an inverted image

A

image is upside down compared to object

21
Q

in what scenario would an image appear magnified?

A

when an object is placed inside the focal length of a converging/convex lens (but a virtual image)

22
Q

equation to calculate magnification?

A

image height
______________

object height

23
Q

similarities between concave and convex lenses?

A

S - both can be used both ways

  • both refract light
  • both have a principle focus on both sides of lens
24
Q

differences between concave and convex lenses?

A

D - concave produces only virtual images

- convex produces virtual + real images    - concave refracts light rays outwards
- convex refracts light rays inwards
25
Q

at which point are images formed?

A

where all light rays from a point of an object appear to come together

26
Q

what kind of image is formed from a diverging lens?

A

virtual, upright, diminished

27
Q

what is the principal axis?

A

an imaginary line running horizontally through the middle of the lens

28
Q

why cannot concave lenses produce a real clear image?

A

as the light rays do not focus (so must be dotted backwards)

29
Q

how do you represent a concave lens?

A

\/
|
|
/\

30
Q

how do you represent a convex lens?

A

/\
|
|
\/

31
Q

how does the thickness of lenses affect their focal lengths? (and why)

A

thicker lens = shorter focal length

- as light spends more time travelling through a thicker lens, so would end up being bent more

32
Q

define dispersion

A

separating a ray/ a wave (usually of white light) into its individual wavelengths/frequencies

33
Q

why do the different ‘colours’/ wavelengths refract by different amounts in glass?

A

different wavelengths of EM radiaton travel at different speeds within glass

34
Q

in terms of the visible light spectrum colours, which colour is refracted the most/least and why

A

smaller wavelength = more refraction

blue light refracted the most, red light refracted the least

(blue light slows down the most, red light slows down the least)

35
Q

in terms of absorption, why would an object appear blue under white light?

A

as it reflects only the frequency of blue, but absorbs all other frequencies of white light (ie. red, green, yellow)

36
Q

what are the 2 ways surfaces can reflect light rays (and what does that depend on)?

A

specular reflection

diffuse scattering
- depends on the type of material (smoothness)

37
Q

what kind of image does specular reflection produce?

  • give example material
  • and why does it do that
A

sharp images
- plane mirror

  • as a mirror obeys the law of reflection and so the parallel rays interacting with the mirror leave parallel to it (in a uniform direction)
38
Q

what kind of image does diffuse scattering produce?

  • give an example of a material which has this
  • and why it does this
A

no images
- sheet of paper

  • paper scatters light rays (causes light rays to leave at non-parallel angles)
  • so light cannot be focused to make an image
39
Q

how does a filter appear red?

A

as it absorbs all the other frequencies, and only allows the frequency of red light to pass through

40
Q

what is black?

A

not an actual colour, only the absence of light/ a certain wavelength of light

41
Q

is white light a colour?

A

no, it is a combination of all the wavelengths and colours

42
Q

all frequencies of light travel at the same speed in a ……….. however, different frequencies travel at different speeds in ….. ………

A 
vacuum 
any medium (ie. glass, water)
43
Q

what happens if a light ray enters a medium perpendicular to the boundary?

A

it carries on in a straight line (no direction change, as it is already at the normal)

44
Q

how will glass interact with UV radiation?

A

absorb it

45
Q

how will glass interact with IR radiation?

A

reflect it

46
Q

what causes light to spread out creating a rainbow effect once it passes through a prism?

A
  • different wavelengths in light refract different amounts because different wavelengths all travel at different speeds
  • it also hits glass at an angle
47
Q

what happens if a light ray enters glass at an angle?

A

part of the wave that hits the boundary first gets slowed down before the rest (changes angle of whole ray)

P5-P8 (11 decks)

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