Case Study: Refraction, Prism, and Snell's Law

Question 1

When white light passes through a glass slab, it does not show dispersion, while it shows dispersion when it passes through a glass prism. Why?

Accepted Answer

0. In a glass slab, opposite faces are parallel, so the dispersion at the first surface is recombined at the second surface. In a prism, non-parallel refracting surfaces cause different wavelengths to bend at different angles permanently, producing a spectrum.

Question 2

Why do we get spectrum when white light passes through tiny water droplets present in air?

Accepted Answer

0. Tiny water droplets act like small prisms, causing refraction, dispersion, internal reflection, and refraction again, splitting sunlight into rainbow colours.

Question 3

Calculate the speed of light in a given medium if angle of incidence in air is $60^\circ$ and angle of refraction in the medium is $30^\circ$. Given that speed of light in air is $3 	imes 10^8	ext{ m/s}$.

Accepted Answer

173205080. By Snell's Law: $$n = \frac{\sin i}{\sin r} = \frac{\sin 60^\circ}{\sin 30^\circ} = \frac{\sqrt{3}/2}{1/2} = \sqrt{3} \approx 1.732$$ Speed of light in medium $v = \frac{c}{n} = \frac{3 	imes 10^8}{\sqrt{3}} = \sqrt{3} 	imes 10^8	ext{ m/s} \approx 1.732 	imes 10^8	ext{ m/s}$.

Case Study: Refraction, Prism, and Snell's Law

Passage / data set

Question 1 of 3

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Question 2 of 3

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Question 3 of 3

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