Question

The refractive indexes of kerosene, turpentine and water are 1.44 , 1.47 , 1.33 respectively . Prove that the light will travel fastest in lowest refractive index materials.

Please answer fast. It's important.

Answer 1

Refractive Index is a constant for a particular material and is an indicator of the speed of light in the given material. The lower the value of the refractive index, faster the speed of light. Vacuum has a refractive index of 1 and light travels at a speed of 300,000,000 metres per second in it.

 

The refractive Index (n) is calculated as follows:

 

n = speed of light in vacuum / speed of light in the medium

 

Lower the value, faster the speed of light in the medium.

 

Since turpentine has the largest value of RI, light will travel the slowest in it. On the other hand, water has a lower RI and will allow light to pass through it at a speed greater than that in either kerosene or turpentine.

Answer 2

Speed of light in a medium $=\frac{c}{n} =\frac{3\times 10^8 ms^{-1}}{n}$

Since the refractive index of water (1.333) is less than the refractive indices of kerosene and turpentine, so light travels faster in water than in kerosene and turpentine.

Since turpentine has the largest value of RI, light will travel the slowest in it. On the other hand, water has a lower RI and will allow light to pass through it at a speed greater than that in either kerosene or turpentine.

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