Refraction Of Light at Plane Surfaces Flashcards
define refraction
the change in the direction of the path of light, when it passes from one transparent medium to another transparent medium. it is a surface phenomenon
(Willebrod Snell’s laws) what are the laws of refraction
- the incident ray, refracted ray, and normal at the point of incidence, all lie on the same plane
- the ratio of the sine of the angle of incidence i andd the sine of angle of refraction r is constant for a given pair of media i.e, mathematically. (the constant is called refractive index)
define refractive index
the refractive index of second medium with respect to the first medium is defined as the ratio of the sine of angle of incidence in the first medium to the sine of angle of refraction in second medium
relationship bw wavelength and speed of light
directly proportional
define absolute refractive index
the refractive index of a medium is defined as the ratio of speed of light in vacuum to speed of light in that medium. (always greater than 1)
condition for a light ray to pass undeviated during refraction
- angle of incidence is 0
- refractive index of medium 2 = medium 1
factors affecting refractive index of a medium
- nature of medium
- physical conditions like temperature (inverse)
- colour of wavelength of light
speed of different colours of light
red- maximum speed, least refractive index
violet- least speed, maximum refractive index
lateral displacement depends on
- thickness of block/ medium
- angle of incidence
- refractive index of medium
- wavelength of light used.
define prism
a prism is a transparent medium bounded by five plane surfaces with a triangular cross section
factors affecting angle of deviation in a prism
- angle of incidence
- material of prism
- angle of prism
- colour or wavelength of light
when is angle of deviation minimum
when angle of incidence is equal to angle of emergence
if the prism ABC is equiangular…
for r1=r2, the ray inside the prism is parallel to base
dependence of angle of deviation on angle of incidence
as i increases, d decreases till it reaches a minimum value. after the minimum, d goes on increasing as i increases.
dependence of angle of deviation of refractive index of prism
higher the RI, higher the deviation. (flint glass has more deviation than crown glass)
dependence of angle of deviation on wavelength
more the wavelength, lesser the deviation
formula for apparent depth
real depth/ refractive index of medium
shift by which object appears to be raised depends on
- refractive index of medium
- thickness of denser medium
- wavelength of incident light (inverse)
define critical angle
critical angle is the angle of incidence in the denser medium corresponding to which the angle of refraction in the rarer medium is 90 degrees.
refractive index of glass with respect to air
1/ refractive index of air with respect to glass
(reciprocal in all cases)
relationship between critical angle and refractive index
refractive index of glass= 1/ sin C
factors affective critical angle
- colour/wavelength of light (least for violet, most for red), critical angle increases with wavelength
- temperature (direct)
how is critical angle related to RI
inversely proportional
define total internal reflection
when a ray of light travelling in a denser medium, is incident on the surface of the rarer medium at an angle of incidence greater than critical angle for the pair of media, the ray is totally reflected back into the denser medium. it reflects 100% of light unlike plane mirrors.
