The speed of light in a medium is inversely related to its refractive index: the lower the refractive index, the faster light travels through the medium. Among kerosene, turpentine, and water, water has the lowest refractive index (approximately 1.33). Kerosene and turpentine have higher refractive indices, around 1.4 and 1.47 respectively. Therefore, light travels fastest in water compared to kerosene and turpentine due to its lower refractive index.

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Introduction to Light Speed in Different Media

Fundamentals of Light Propagation: The speed at which light travels through a medium is determined by the medium’s refractive index. The lower the refractive index, the less the light is slowed down, and thus, the faster it travels through that medium.

Understanding Refractive Index

Indicator of Light Speed: The refractive index of a substance is a measure of how much it reduces the speed of light compared to its speed in a vacuum. A lower refractive index means light can travel through the medium more quickly.

Refractive Indices of Common Liquids

Comparing Kerosene, Turpentine, and Water: Among the given liquids – kerosene, turpentine, and water – each has a different refractive index. Water typically has a refractive index of about 1.33. Kerosene’s refractive index is around 1.4, and turpentine’s is approximately 1.47.

Light Speed in Water

Fastest in Water: Given these refractive indices, light travels fastest in water. Its lower refractive index compared to kerosene and turpentine means that light is less slowed down in water.

Light Speed in Kerosene and Turpentine

Comparatively Slower: In kerosene and turpentine, the higher refractive indices indicate that light travels slower in these liquids compared to water. The denser the medium (in terms of optical density), the more it slows down the light.

NCERT Solutions App

Optimal Medium for Light Speed: Therefore, among kerosene, turpentine, and water, light travels fastest in water due to its lowest refractive index. This principle is crucial in understanding the behaviour of light in different environments and has practical applications in optics and photonics.

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Questions of 10th Science Chapter 9 in Detail

Define the principal focus of a concave mirror.
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Name a mirror that can give an erect and enlarged image of an object.
Why do we prefer a convex mirror as a rear-view mirror in vehicles?
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located?
A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass?
Find out, from Table, the medium having highest optical density. Also find the medium with lowest optical density.
You are given kerosene, turpentine and water. In which of these does the light travel fastest?
The refractive index of diamond is 2.42. What is the meaning of this statement?
Define 1 dioptre of power of a lens.
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Find the power of a concave lens of focal length 2 m.
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror?
Name the type of mirror used in the following situations. (a) Headlights of a car. (b) Side/rear-view mirror of a vehicle. (c) Solar furnace.
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An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. What is the position, size and the nature of the image formed.
A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens?
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
The magnification produced by a plane mirror is +1. What does this mean?
An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focussed image can be obtained?
Find the focal length of a lens of power – 2.0 D. What type of lens is this?
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?