Question

(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vacuum.

(b) The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is , calculate the speed of light in:

(i) vacuum,

(ii) medium 'A'.

Solution

Laws of refraction states that:

(1) The incident ray, the refracted ray and the normal to the interface of two media at the point of incidence all lie in the same plane.
(2) For the light of a given color and for given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

This is also known as Snell's Law.

Mathematically it can be written as:
$fraction numerator sin space straight i over denominator sin space straight r end fraction space equals space c o n s tan t space equals space mu presuperscript A subscript B$

Here, $straight mu$ is the refractive index of medium B with respect to medium A.

Refractive index of a medium with respect to the vacuum is known as the absolute refractive index.

$straight mu subscript straight B space equals straight c over straight v semicolon$ c is the speed of light in vacuum and c is the speed of light in medium B.

b) Absolute refractive of medium A, $straight mu subscript straight A$ =2

Absolute refractive index of medium B, $straight mu subscript straight B$ =1.5

$straight i right parenthesis space For space medium space straight B comma 1.5 space equals space fraction numerator straight c over denominator 2 space straight x space 10 to the power of 8 end fraction rightwards double arrow space straight c space equals space 2 space straight x 1.5 space straight x space 10 to the power of 8 rightwards double arrow space straight c equals space 3 space straight x space 10 to the power of 8 Speed space of space light space in space vaccum space is space 3 space straight x space 10 to the power of 8 ii right parenthesis space For space medium space straight A comma space straight mu subscript straight A space equals straight c over straight v rightwards double arrow space straight v equals straight c over μA straight v equals fraction numerator space 3 space straight x space 10 to the power of 8 over denominator 2 end fraction space equals 1.5 space straight x space 10 to the power of 8 space is space the space required space speed space of space light space in space medium space straight A comma.$

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Acids, Bases And Salts

Some More Questions From Acids, Bases and Salts Chapter

What do you mean by reflection, refraction and absorption of light?

Which type of phenomenon (reflection or refraction) occurs when light falls on (i) a highly polished surface like a mirror and (ii) a transparent medium like glass or water?

What is meant by the optical image of an object?

What are real and virtual images? Can these images be obtained on a screen? Give reasons in support of your answer.

Give three points of differences between real and virtual images.

What is a mirror? Mention the different types of mirrors commonly used.

Define the following terms in connection with reflection of light:
Incident ray, reflected ray, point of incidence, normal, angle of incidence and angle of reflection.

State the laws of reflection of light.

Are the laws of reflection applicable to plane surfaces also valid for curved surfaces?

State the important properties of images formed by plane mirrors.

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