Light Flashcards
Speed of light in vacuum
3.00 x 10^8 m s^-1
c in n=c/v
Speed of light in vacuum
n in n=c/v
Refractive index of medium
(Usually reserved for absolute refractive index)
v in n=c/v
Speed of light in medium
How to get absolute refractive index
n = c/v
“c” is the speed of light in a vacuum,
“v” is the speed of light in the material
“n” is the index of refraction.
Snells law
(Refractive index of a)(sin angle of incidence) =
(Refractive index of b)(sin angle of refraction)
nA sin 0A = nB sin 0B
What angle is the same as critical angle
angle of incidence
whats the critical angle
when light exits an optically denser medium at a specific angle of incidence known as the critical angle, the maximum angle of refraction of 90deg to the normal(flat) takes place
critical angle formula
sin^-1* (n2/n1)
n2 is the refractive index of the less dense medium
n1 is the refractive index of the denser medium
this si because critical angle occurs from when light travels from an optically denser medium to an optically less dense medium
how can u use depth to calculate refractive index
n = real depth/apparent depth
whats the relationship focal length((f), distance of object from lens (u) and distance of image from lens(v) have
and whats different for virtual images
1/f = 1/u + 1/v
in virtual images the v is a negative number
f in 1/f = 1/u + 1/v
focal length
u in 1/f = 1/u + 1/v
distance of object from lens
v in 1/f = 1/u + 1/v
distance of image from lens
if the object is beyond 2f, what is the properties of the image
real, inverted, diminished
if the object is 2f, what is the properties of the image
real, inverted, equal
if the object is between 2f and f, what is the properties of the image
real, inverted, magnified
if the object is f, what is the properties of the image
no image as no light converges
if the object is between f and o, what is the properties of the image
virtual, upright, magnified
magnification formula
M = v/u
distance of object from lens (u)
distance of image from lens(v)
whats the requirements for light to refract
different mediums shouldve have different absolute refractive indices. if 2 mediums have similar absolute refractive indices, the speed of light will not change in them and light would not refract or bend
whats a condition needed for critical angle to occur
light travels from an optically denser medium to an optically less dense medium
pro air time skip for snells law
air is a
other medium is b
n.b = sinθa / sinθb
(refractive index of 2nd medium) =
(sin incidence from air)/(sin refractive out to 2nd medium)
uses of a glass prism vs mirror or polished surface
- surface does not corrode like a silver surface
- light energy is fully reflected at the boundary.
- multiple reflections are not an issue with prisms
- can be made to fit into smaller optical equipment where mirrors cannot be effectively used.
describe optic fibres
optic fibres make use of total internal reflection to transmit light signals. Multiple total internal reflection takes place along the entire length of the uniform glass fibre that is layered with an optically less dense material. however, booster units are needed to enhance the light signal after some distance
principle of reversibility
light will retrace its path when you reverse the light
magnification formula by (distance between object and lens) and (distance between image and lens)
M = v / u
what do parallel rays signify usually
light rays from infinity
how to find the focal point for a infinity ray graph with no information other than 2 parrallel rays coming down
the point where they converge is the focal length, below/ above = to the focal point
Less dense to dense, where will light bend towards
it slows down and bends towards the normal.
Denser to less dense, where will light bend towards
it speeds up and bends away from the normal.
define absolute refractive index
the ratio of speed of light in vacuum (c), to that of the speed of light in medium (v),
range of values of absolute refractive index
the absolute refractive index is always greater than 1
what is the relative refractive index
it is the ratio between 2 absolute refractive indexes
or
speed of light in 2 mediums
how to get the relative refractive index
n2/n1
asolute refractive index
n2 (entering medium) / n1 (leaving medium)
or
v1/v2
speed of light
v2 (entering medium) / v1 (leaving medium)
The speed of light in a medium is inversely proportional to its refractive index.
(range of values/ratio) of relative refractive index
relative refractive index may be greater than or smaller than unity(1:1)