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Lenses can be used to help people see clearly - OCR Gateway - GCSE Physics - Question 18 - 2019 - Paper 1
Question 18
Lenses can be used to help people see clearly. Fig. 18.1 is a diagram of a convex lens. (a)(i) A student models the lens using two glass prisms and a glass block. ... show full transcript
Worked Solution & Example Answer:Lenses can be used to help people see clearly - OCR Gateway - GCSE Physics - Question 18 - 2019 - Paper 1
Step 1
A student models the lens using two glass prisms and a glass block.
Answer
To complete the ray diagram (Fig. 18.2), draw two parallel lines representing light rays coming from the left. The first ray enters the first glass prism at a slight angle, refracting towards the base of the prism. When it exits the prism, it should bend further towards the centerline of the diagram. The second ray follows the same path through the second prism before reaching the glass block. The light rays converge and are shown meeting at a focal point after passing through the glass block.
Step 2
Explain how a convex lens can correct long-sighted vision.
Answer
A convex lens helps correct long-sighted vision by converging light rays before they enter the eye. When light rays from distant objects enter the eye directly, they focus behind the retina due to the eye's shape. The convex lens bends these rays inwards, ensuring that they meet on the retina. This adjustment allows the individual to see objects clearly at both distances, effectively resolving long-sightedness.
Step 3
What colour does the red paper appear in blue light?
Answer
In blue light, the red paper appears black. This is because red paper reflects red wavelengths of light but absorbs other colors, including blue. Therefore, when illuminated with blue light, the red paper does not reflect any light back to the observer, making it appear black.