Solutions-Class 10-Science & Technology-1-Chapter-6-Refraction of Light -Maharashtra Board

(i) Refractive index depends on the wavelengthof light.
(ii) The change in directionof light rays while going from one medium to another is called refraction.

In the fig SR || PQ and OM is the reflected ray Hence r₁=r₂

Let μ be the refractive index of the glass slab.

Then, according to Snell's law,

\(\frac{sin\,\,i}{sin\,\, r_1}\) = μ    .....(i)

and

\(\frac{sin\,\,r_2}{sin\,\, e}\) = \(\frac{1}{μ}\) .... .....(ii)

But r₁=r₂

Putting (iii) in (i), we get

\(\frac{sin\,\,i}{sin\,\, r_2}\) = μ .....(iv)

Multiplying (ii) and (iv), we have

\(\frac{sin\,\,i}{sin\,\, r_2}\) x \(\frac{sin\,\,r_2}{sin\,\, e}\) = μ x \(\frac{1}{μ}\) 

∴ \(\frac{sin\,\,i}{sin\,\, e}\) = 1

∴ i = e proved

The rainbow formation in the sky is the combined effect of the refraction, dispersion, and total internal reflection of light.

(1) The sunlight is a mixture of seven colours,. The atmosphere contains a large number of water droplets after raining stopped.

When sunlight is strike on a water droplet, there is

• refraction and dispersion of light as it passes from air to water
• internal reflection of light inside the droplet and
• refraction of light as it passes from water to air.

(2) The refractive index of water is different for different colours, being maximum for violet and minimum for red. Hence, there is dispersion of light into different colours as it passes from air to water. As shown in Fig

(3) The combined action of different water droplets, acting like tiny prisms, is to produce a rainbow with red colour at the outer side and violet colour at the inner side. The remaining five colours lie between these two.

We see the rainbow when the sun is behind the us and water droplets in the front.

The correct reason for the twinkling of stars is changing refractive index of the atmospheric gases. The correct answer is option (iv).

We can see the Sun even when it is little below the horizon because of refraction of light. Correct option is (ii)

Refractive index of air with respect to glass is 2/3. The correct answer is option (iv).

C = 3×10⁸ m/s , v=1.5×10⁸ m/s

Absolute refractive index of a medium, 

μ=Speed of light in air/Speed of light in the medium = c/v

⇒μ=\(\frac{3×10^8}{1.5×10^8}\) = 2

2 is the absolute refractive index of the medium

μ_g=3/2 and μ_w=4/3 μ_gw=?

where, 
μ_gw=Refractive index of glass w.r.t. water

μ_g=Absolute refractive index of glass

μ_w=Absolute refractive index of water

Now,
μ_g=3/2 and μ_w=4/3

μ_gw = \(\frac{μ_g}{μ_w}\)= \(\frac{3}{2}\) x \(\frac{3}{4}\) = 9/8

9/8 is Refractive index of glass w.r.t. water