Lecture 2 - Refraction Flashcards

1
Q

What is refraction

A

when a wave or light ray moves from one medium to another e.g. air/glass/water causing speed and direction to change

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2
Q

What does refraction cause

A

Bending of light - wavefront tilted

= changes direction

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3
Q

What happens when light travels from a fast medium to a slow medium
e.g. air to glass/water

A

Refractive index of glass HIGHER than air
SLOWS down, ray of light TOWARDS normal
Angle of refraction < angle of incidence

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4
Q

What happens when light travels from a slow medium to a fast medium
e.g. glass/water to air

A

SPEEDS UP
ray of light AWAY from normal
Angle of refraction > angle of incidence

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5
Q

Whats the rule for rays and wavefronts

A

Rays and wavefronts are 90 degrees/ perpendicular to each other

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6
Q

How do ripples work

A

Stone in pond
Starts circular and steep
Less steep as wavefronts move away
Eventually flat and parralel lines, less circular large distance away

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7
Q

Where do ripples of water travel

A

Outwards

Away from where rock fell in water

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8
Q

What is the refractive index formula

A
n = c/v
c = speed of light in vaccum
v = speed of light in medium
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9
Q

is n negative or positive number

A

positive

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10
Q

what is snells law formula

A
n sin i  = n' sin i'
n = refractive index before refraction
i = angle of incidence 
n' = refractive index after refraction
i' = angle of refraction
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11
Q

what is prism

A

correct squint - moves object so it goes onto fovea

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12
Q

How to correct squints

A
  • Object moved towards angle of prism
  • Control how much it moves by how big angle is
  • Also swap direction - rotate it
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13
Q

Dispersion in rainbow

A

different wavelengths dispersed = rainbow = different colours
shine white light

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14
Q

Does it travel faster or slower in middle of lens and why

A

slower

because thicker

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15
Q

what part of wavefront hits lens first

A

middle before edges

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16
Q

where do spherical wavefronts converge to

A

focal point

17
Q

what does a shorter focal length show

A

F closer to lens but power of lens increases

18
Q

Equation for working out power

A
F = 1/f
F = surface power 
f = focal point
19
Q

what is object distance ( I )

A

Distance of object FROM lens axis

20
Q

what is image distance ( I’ )

A

Distance of image from lens axis

21
Q

what is focal length (f )

A

Distance of focal point from lens axis

22
Q

what is surface power ( F )

A

power of lens

23
Q

what is focal point ( F’ )

A

point on optical axis where rays meet

24
Q

Is distance form surface(lens) to object negative or positive

A

negative

25
Q

Is distance from surface ( lens ) to image negative or positive

A

positive

26
Q

what does the lens equation show

A

equation for distance between lens, image and distance

27
Q

what is lens equation

A
1/l' = 1/l + 1/f
l' = image distance
l = object distance
f = focal length
28
Q

formula for magnification

A

l’/l

size of image/size of object

29
Q

does light move slower in air or glass

A

glass

30
Q

what is index of refraction for light in a vaccum

A

1