The correct option is A is true but R is false
Explanation
Refraction is the phenomenon where a light ray changes its direction when passing from one transparent medium to another due to a change in its speed.
- Assertion (A) is Correct: Air is an optically rarer medium, while glass is an optically denser medium. When a ray of light travels from a rarer medium to a denser medium, its speed decreases. Consequently, the ray bends towards the normal at the interface.
- Reason (R) is Incorrect: The speed of light in a medium is inversely proportional to the optical density (refractive index) of that medium ($v \propto 1/n$). Since glass is optically denser than air (refractive index of glass $\approx 1.5$ vs. air $\approx 1.0$), the speed of light is lower in glass than in air.
Key Takeaway: Light bends towards the normal when entering a denser medium because its velocity decreases. Conversely, it bends away from the normal when entering a rarer medium because its velocity increases.