Questions & Answers

Light travels ___________(Faster, slower) in air, but_________ (Faster, slower) in glass.
A. Faster, faster respectively
B. Slower, faster respectively
C. Faster, slower respectively
D. None

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Hint:An optically denser medium is the one that eventually slows down or reduces the velocity of the incident wave when the incident wave falls on that medium whereas an optically rarer medium is one that speeds up or eventually causes the wave to pass through it faster than in the medium it was previously in. Using this information, we can find out the correct answer.

Complete answer:
As we know, $v$ is equal to the speed of light in any medium. $c$ is equal to the speed of light in the vacuum. $\mu $ is equal to the permeability of the medium. The relation between the above 3 constants is given by –
\[v = \dfrac{c}{\mu }\]
Value of $c$ is constant that is $3 \times {10^8}m/s$ thus $v \propto \dfrac{1}{\mu }$
As the refractive index of the medium increases, the speed of light in the medium decreases.The refractive index of glass is higher than air, so the speed of light will be slower in glass and faster in air.

Hence, option C is the correct answer.

Note:Light travels faster in rarer medium and relatively slower in optically denser medium. The optically rarer medium is a medium which slows down the electromagnetic wave and the optically denser medium is a medium which fastens the electromagnetic wave. Light is a kind of electromagnetic wave that is visible to the human eyes. As an incident wave of light passes from an optically rarer to an optically denser medium the ray or wave of light bends more towards the normal at the interface and vice versa.