 When a ray of light travels from air into water, it bends towards the normal. This occurs due to the decrease in light’s speed as it moves from a less dense medium (air) to a denser medium (water). According to Snell’s Law, the change in speed causes the light to refract, and the bending towards the normal is a result of the light slowing down in the denser medium.

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## Introduction to Refraction

Understanding Light’s Behaviour: Refraction is the bending of light as it passes from one medium to another with a different density. This phenomenon is governed by Snell’s Law and is a fundamental concept in optics.

### The Nature of Light

Speed Variations: Light travels at different speeds in different media. It moves faster in less dense mediums like air and slower in denser mediums like water. This change in speed is what causes refraction.

#### Transition from Air to Water

Entering a Denser Medium: When a ray of light travels from air (less dense) into water (more dense), it experiences a decrease in speed. This sudden change as it enters the water causes the light ray to bend.

##### Bending Towards the Normal

Direction of Refraction: As per the principles of refraction, when light enters a denser medium, it bends towards the normal. The normal is an imaginary line perpendicular to the boundary between the two media at the point of incidence.

###### Explanation through Snell’s Law

Optical Law Governing Refraction: Snell’s Law quantitatively describes the relationship between the angles of incidence and refraction and the indices of refraction of the two media. It predicts that light will bend towards the normal when entering a denser medium because the angle of refraction is smaller than the angle of incidence.

Behaviour of Light in Different Media: Thus, when a ray of light traveling in air enters obliquely into water, it bends towards the normal. This bending is a consequence of the light slowing down as it moves from a less dense medium (air) to a denser medium (water), a fundamental characteristic of the refraction of light.

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Questions of 10th Science Chapter 9 in Detail

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