Q.1. What is meant by Refraction? Why does this take place ?
A. The bending of light rays, as it travels from one medium to another having different refractive indices, is called refraction of light.
The phenomenon of refraction takes place because of difference in the speed of light in different media.
For eg, Light travels with 3x10^8 m/s in vacuum or air , 2x10^8 m/s in glass and 2.25x10^8 m/s in water.
Q.2. Is optical density and density same ? Explain.
A. No. Optical density and density are not the same physical quantities.
Optical density is measured by the speed of light in that medium, whereas, density is the mass contained per unit volume.
For eg, Kerosene floats above water suggesting that it is lighter than water, i.e. its density is lower than that of water. But the refractive index of kerosene is 1.44 whereas that of water is 1.33, suggesting that kerosene is optically denser than water.
Q.3. What are the factors on which refractive index of a medium depends ?
A. The factors on which refractive index of a medium depends are :
i. Nature of the medium, in other words its optical density. More is the optical density, more is its refractive index, and hence, less is the speed of light in it.
ii. Colour of the light used or the wavelength. Red light, having largest wavelength in the visible region, shows lowest refractive index and hence, bends less. Violet, having shortest wavelength, shows highest refractive index, and hence, bends more.
iii. Temperature. Due to increase in temperature the density of the medium decreases, so light moves fast through it. As a result decreases.
A. The bending of light rays, as it travels from one medium to another having different refractive indices, is called refraction of light.
The phenomenon of refraction takes place because of difference in the speed of light in different media.
For eg, Light travels with 3x10^8 m/s in vacuum or air , 2x10^8 m/s in glass and 2.25x10^8 m/s in water.
Q.2. Is optical density and density same ? Explain.
A. No. Optical density and density are not the same physical quantities.
Optical density is measured by the speed of light in that medium, whereas, density is the mass contained per unit volume.
For eg, Kerosene floats above water suggesting that it is lighter than water, i.e. its density is lower than that of water. But the refractive index of kerosene is 1.44 whereas that of water is 1.33, suggesting that kerosene is optically denser than water.
Q.3. What are the factors on which refractive index of a medium depends ?
A. The factors on which refractive index of a medium depends are :
i. Nature of the medium, in other words its optical density. More is the optical density, more is its refractive index, and hence, less is the speed of light in it.
ii. Colour of the light used or the wavelength. Red light, having largest wavelength in the visible region, shows lowest refractive index and hence, bends less. Violet, having shortest wavelength, shows highest refractive index, and hence, bends more.
iii. Temperature. Due to increase in temperature the density of the medium decreases, so light moves fast through it. As a result decreases.
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