Refraction of Light Rays, Examples and Solutions 

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Refraction of Light Rays at Interfaces
Light rays travel in different mediums at different speeds. In vacuum, for example, light travels at the speed of 3×10^{8} m/s. This is the highest speed possible in physics.
n = c / v Example 1What is the index of refraction in a medium where the speed of light is 1.5×10^{8} m/s? Solutionn = c / v = 3×10^{8} m/s / 1.5×10^{8} m/s = 2 Example 2What is the speed of light in water whose refractive index is 1.33? Solution
1.33 = 3×10^{8} m/s / v
Snell's Laws of refraction
A homogeneous medium has a constant index of refraction throughout the medium and light travels along straight paths in it.
Refraction occurs at the interface or boundary of two media with different refractive indices. It is the bending of light rays when transmitted into the second medium.(see diagram below)
n_{1} sin (i) = n_{2} sin (t) where n _{1} is the refractive index of medium (1), n _{2} is the refractive index of medium (2), i is the angle of incidence and t is the angle of refraction as shown in the diagram above. Refraction explains physical phenomena such the appearance of a pen bent inside a glass of water and the separation of white light into different colors such as the rainbow as shown below. Example 3
A ray of light is incident through glass, with refractive index 1.52, on an interface separating glass and water with refractive index 1.32. What is the angle of refraction if the angle of incidence of the ray in glass is 25 °?
Solution
Use Snell's law to write: 1.52 sin 25° = 1.32 sin t
Example 4
What should be the angle of incidence of a light ray incident through air on the boundary separating air from water so that the angle of refraction is 30 °?(refractive index of air is 1 and that of water is 1.32)
Solution
Assume refractive index of air is equal to 1.
Example 5
A light ray strikes a homogeneous rectangular block of glass of thickness w at an angle i. The ray emerges at point B at an angle i'. (see diagram below)
Solution
a) Snell's at point A
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