Rays of light pass through the transparent cover of the headlight. Which diagram shows how a ray of light passes through the transparent cover?

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Consider the rules of refraction. When light enters a denser medium (like glass) from a less dense medium (like air), it slows down and bends towards the normal. When it leaves the denser medium and re-enters the less dense medium, it speeds up and bends away from the normal. The emergent ray should be parallel to the path the incident ray was on.

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B.<svg width='150' height='100' viewBox='0 0 150 100'><rect x='60' y='10' width='30' height='80' fill='#e0e0e0' stroke='black'/><path d='M10,30 L70,50 L140,70' stroke='black' stroke-width='2' fill='none' marker-end='url(#arrow)'/></svg>✓ Correct

The correct diagram is the second one. The ray of light bends towards the normal as it enters the block and away from the normal as it leaves. The emergent ray is parallel to the incident ray but has been displaced sideways.

When a ray of light passes through a parallel-sided transparent block: 1. **Entering the block:** Light travels from a less dense medium (air) to a more dense medium (glass/plastic). It slows down and refracts (bends) **towards** the normal. 2. **Leaving the block:** Light travels from the more dense medium back into the less dense medium. It speeds up and refracts **away** from the normal. The result is that the emergent ray is parallel to the incident ray, but it has been shifted sideways. This is known as lateral displacement. Diagram B correctly illustrates this.

Common mistakes

✗ Choosing diagram A, which shows no refraction.\n✗ Choosing diagram C, which shows the light bending the wrong way (away from the normal) as it enters the block.

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Rays of light pass through the transparent cover of the headlight. Which diagram shows how a ray of light passes through the transparent cover?

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Practice the full AQA GCSE Physics Higher Tier Paper 2

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