Question

State the laws of refraction of light, if the speed of light in vacuum is 3×10⁸ m,/s find the speed of light in a medium of absolute refractive index 1.5.​

Answer 1

Answer:

There are two laws of refraction of light :

1. The incident ray, reflected ray and normal ray at the point of incidence, all will lie in the same plane.
2. Sine of angle of incidence (i) to the sine of angle of refraction (r), ratio is constant(n) , n = sin I/sin r. [This law is also known as snell's law].

______

Given :

• Speed of light in vacuum is 3 × 10⁸ m/s.
• Refractive index is 1.5.

To find :

• Speed of light in a medium of refractive index.

Solution :

We know,

Refractive index of the medium →

Speed of light in vacuum/ Speed of light medium

So,

→ Speed of light medium = Speed of light in vacuum/Refractive index

→ Speed of light in medium = 3 × 10⁸/1.5

→ Speed of light in medium = 30 × 10⁸/15

→ Speed of light in medium = 2 × 10⁸

Thus,

Speed of light in medium of refractive index is 2 × 10⁸ m/s.

Answer 2

Given :-

if the speed of light in vacuum is 3×10⁸ m/s

absolute refractive index 1.5.​

To Find :-

Speed of light in medium

Solution :-

1]

Snell Law - It states the relationship between between the angles of incidence and refraction,

Formula

$\sf \dfrac{\sin\theta_{2}}{\sin\theta_{1}} = \dfrac{n_1}{n_2} = \dfrac{v_2}{v_1}$

2]

ng = c/v

Refractive index = ng

Speed of light in vacuum = c

Speed of light in medium = v

1.5 = 3 × 10⁸/v

1.5v = 3 × 10⁸

v = 3 × 10⁸/1.5

v = 2 × 10⁸ m/s

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