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Applications on the total reflection of light

From Online Sciences - October 20, 2017

Light refraction is used in explaining total reflection and dispersion of white light , When a light ray travels from an optically higher dense medium ( such as water ) to an optically less dense one ( such as air ) , it refracts away from the normal line , As the angle of incidence increases in the optically higher dense medium , the angle of refraction increases in the optically less dense one .

Total reflection

At a certain angle of incidence , the angle of refraction reaches its maximum value , which is 90 and the light emerges tangent to the separating surface and is called in this case grazing ray , the angle of incidence is called the critical angle ( c ) .

When the angle of incidence exceeds the value of the critical angle , the light ray does not emerge to the optically less dense medium but reflects totally in the optically higher dense medium and this phenomenon is called total reflection .

Critical angle between two media ( c ) is the angle of incidence in the optically higher dense medium , which corresponds to an angle of reflection in the less dense medium equals90 .

Total reflection is the reflection of the light rays in the optically higher dense medium when the angle of incidence exceeds the critical angle of the optically higher dense medium .

When the critical angle of a medium with air = 40 , This means that the angle of incidence in this medium = 40 , corresponds an angle of refraction in air = 90 .

Conditions of the total reflection

Deduction of the relation between the sine of the critical angle & the refractive index of a medium

Applying Snells law :

n1 sin= n2 sin

= c ,= 90

n1 sin c = n2 sin 90

sinc=n2 / n1 = 1n2

Where ( n ) is the absolute refractive index of the optically higher dense medium .

Applications on the total reflection of light

Optical fibers ( fiberoptics )

Optical fibers uses

Reflecting prism

Mirage

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