(A) The speed of light in glass is 2×10 m/s and in water 5 2,25×10 m/s. (a) Which one of the two is optically denser and why? (b) A ray of light is incident normally at the water-glass interface when will happen to the path of the ray after entering the glass? Give reason.

Question :(A) The speed of light in glass is 2×10 m/s and in water 5 2,25×10 m/s.
(a) Which one of the two is optically denser and why?
(b) A ray of light is incident normally at the water-glass interface when will happen to the path of the ray after entering the glass? Give reason.

The correct answer is -(a) Glass is optically denser because its refractive index (n) is greater than the refractive index of water. Refraction index of glass (n₁) = speed of light in vacuum/speed of light in glass = 3×10^8/2×10^8 = 1.5 Refraction index of water (n₂) = speed of light in vacuum/speed of light in water = 3×10^8/2.25×10^8 = 1.33 As n₁ > n₂, glass is optically denser.

(b) The path of the ray of light will bend towards the normal when it enters the glass. This is because the speed of light is lower in glass than in water, which causes the light to slow down and bend towards the normal. The normal is a line perpendicular to the surface of the water-glass interface. The angle of incidence and the angle of refraction will depend on the refractive indices of both media and can be calculated using Snell’s law.