Lenses

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A lens is a transparent medium bound by two surfaces. It can be made of glass or plastic and is used to refract light rays. Most lenses have two surfaces that are parts of spheres, allowing them to co

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Convex lens: Has two spherical surfaces bulging outwards, thicker at the center than at the edges, also called double convex lens. Concave lens: Has two spherical surfaces curving inwards, thinner at

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The optical center (O) is the point inside a lens on the principal axis through which light rays pass without changing their path. Any ray passing through the optical center continues in a straight li

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The principal focus of a convex lens is the point on the principal axis where light rays parallel to the principal axis converge after refraction through the lens. A convex lens has two principal foci

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A convex lens is called a converging lens because light rays parallel to the principal axis converge (come together) at a single point called the principal focus after refraction through the lens.

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A concave lens is called a diverging lens because light rays parallel to the principal axis diverge (spread apart) after refraction. The diverged rays appear to come from a point on the principal axis

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Rule 1: A ray parallel to the principal axis passes through the principal focus after refraction. Rule 2: A ray passing through the principal focus becomes parallel to the principal axis after refract

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When an object is placed beyond 2F₁: Image is formed between F₂ and 2F₂, Real and inverted, Smaller than the object. This is the principle used in cameras.