A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
The light ray bends towards the normal when it enters obliquely from air into water.
This happens because air is a rarer medium while water is a denser medium. When light travels from a rarer medium to a denser medium, it bends towards the normal.
Refraction occurs due to the change in the speed of light as it enters from one transparent medium to another. As light enters water from air, its speed decreases, causing the ray to bend towards the normal.
Explanation
The textbook context clearly states that when a light ray enters from a rarer medium to a denser medium (like air to glass), it bends towards the normal. The same principle applies for air to water since water is optically denser than air. The reason for this bending is the change in speed of light when it moves from one medium to another, which is the fundamental cause of refraction.
Solution Steps
Step 1: Identify that air is a rarer medium and water is a denser medium.
Step 2: Apply the rule from context - light bends towards the normal when entering from rarer to denser medium.
Step 3: State the reason - refraction occurs due to change in speed of light between media.