Refraction
Refraction is the bending of a light wave as it travels from one
medium to another at the interface of media. This happens due to variations in
densities between the two materials which intern change the speed of light when
the light wave passes from one medium to another.
When light wave travels from a
rarer to a denser medium. Its speed reduces resulting it bends towards the normal.
When light wave travels from a
denser to a rear medium. Its speed increases resulting it bends away the normal.
When light passes from one
medium to another, its velocity changes and thus the wavelength also changes but
frequency and its color remain constant.
Laws of refraction
Laws of refraction state that:
The incident ray refracted
ray, and the normal at the point of incidence at the interface of two media all
lie on the same plane.
The ratio of the sine of the
angle of incidence to the sine of the angle of refraction is constant. This constant
is called refractive index of second medium with respect to first medium. This
is also known as Snell's law of refraction.
Refractive index
Refractive index is the ratio
of the velocity of a light ray in an empty space to the velocity of light in a
substance, n = c/v.
The refractive index gives the
measure of bending of a light ray when passes from one medium to another.
Apparent depth
When we look into a tank water filled tank, the bottom of the
tank seems to be raised. This is due to refraction.
The depth of bottom is called apparent depth or virtual depth that is observed as a result of the
refraction of light. The apparent depth / virtual depth depends upon the
refractive index of the medium (material filled in tank).
Red arrow shows the actual depth of coin in water.
Green arrow show the apparent depth of coin.
