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Light refraction , Snell's law , Factors affect the absolute refractive index of a medium

From Online Sciences - October 14, 2017

The light refraction can be used in analyzing a beam of white light into its components of different wavelengths due to difference of the absolute refractive index according to the wavelength of the incident light ray , so , the white light scatters into its components ( seven colours which are different in their wavelength ) and it can be seen in the soap bubbles .

Light refraction

When a light ray falls on a separating surface between two transparent media different in the optical density , Very small part of light is absorbed in the second medium , Part of the light ray reflects in the first medium , The other part passes to the second medium , changing its direction and this phenomenon is known as light refraction .

Conditions of refraction

Light refraction is the change of light path direction when it passes through two transparent media different in the optical density .

Angle of refraction is the confined angle between the refracted light ray and the normal line at the point of incidence on the separating surface of the two media .

Optical density is the ability of the medium to refract the light rays when they pass through it .

The light refraction obeys two laws , which are :

First law : The ratio between the sine of the angle of incidence ( sin) in the first medium to the sine of the angle of refraction ( sin ) in the second medium is equal to the ratio of the speed of light ( V1 ) in the first medium to the speed of light ( V2 ) in the second medium .

The ratio is constant for the two media and is called relative refractive index 1n2 .

1n2 = sin/ sin = V1 / V2

Second law : The incident light ray , the refracted light ray and the normal line at the point of incidence all lie in the same plane which is perpendicular on the separating surface between the two media .

From the first law : sin= sin

When plotting a relation betweensin, sin , we get a straight line , Its slope represents the relative refractive index between the two media .

Slope = sin/ sin = 1n2

Relative refractive index between two media ( 1n2 ) is the ratio between sine the angle of incidence in the first medium to the angle of refraction in the second medium , or it is the ratio between the speed of light in the first medium to the speed of light in the second medium .

When the relative refractive index between the glass and the water = 0.86 , this means that the ratio of the speed of light in the glass to the speed of light in the water = 0.86 .

Factors affect the relative refractive index between two media :

The absolute refractive index of a medium

If the light ray passes from the space or the air to any other transparent medium , The ratio between sine the angle of incidence in the space ( sin) to sine the angle of refraction in the medium ( sin) equals the ratio between the speed of light in the space ( c ) to the speed of light ( v ) in the medium , this ratio is constant for the medium and it is called the absolute refractive index of the medium ( n ) .

n = sin/ sin = V1 / V2

The absolute refractive index of the medium ( n ) is the ratio between sine the angle of incidence in the space to sine the angle of refraction in the medium , or it is the ratio between the speed of light in the space to the speed of light in the medium .

The absolute refractive index of any medium is always more than one , because the speed of light in the space is more than its speed in any other medium , The absolute refractive index has no measuring units , because it is a ratio between two similar physical quantities .

The absolute refractive index of a medium is inversely proportional to the speed of light in this medium ( n1/v ) , When plotting a relation between( sin) in air and( sin) in any medium , we get a straight line , Its slope represents the absolute refractive index ( n ) for this medium .

Slope = sin/ sin = n

Factors affect the absolute refractive index of a medium

The relation between the relative refractive index and the absolute refractive index

Snells law

Explanation of refraction

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