Question

The refractive index of a given piece of transparent quartz is the greatest for
$\left( a \right)$ Red light
$\left( b \right)$ Violet light
$\left( c \right)$ Green light
$\left( d \right)$ Yellow light

Answer 1

Hint:The ratio of the speed of light in vacuum to the speed of light in the medium is termed as refractive index. Refractive index is inversely proportional to wavelength. Using this concept, you can solve this question.

Complete step by step answer:
The ratio of the speed of light in vacuum to the speed of light in the denser medium is termed a refractive index. The refractive index variable is generally indicated by the letter n.

The colours ranging from longest wavelength to shortest are red, orange, yellow, green, blue, indigo, and violet.

The visible light spectrum is the only part of the electromagnetic spectrum that can be seen by the naked human eye with wavelength ranging between about $400nm$ and $700nm$.
The values $1.334$ and $1.334$ are the violet and red colour of the refractive indices of water. The wave or the light of colour of having a greatest wavelength will get less amount of refracted.

So, red with a higher wavelength gets refracted less than violet which has a relatively higher wavelength.

Refractive index increases with decreasing wavelength of light. Of the given lights, violet has the highest frequency hence least wavelength.

So, the refractive index of transparent quartz will be greatest for violet light which has least wavelength.

Hence the correct option $\left( b \right)$.

Note:When white light is made to pass through a triangular prism of a material denser than air (say glass), dispersion occurs. We can observe that violet is at the bottom and red is at the top in this spectrum. So we can perfectly determine that red is less deviated than violet. The transparent quartz refractive index is the least for red colour.