Two converging lenses of focal lengths f₁ and f₂ are placed coaxially in contact. Derive the expression for the focal length of the combination using the ray diagram for the formation of the image of an object by the combination.

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TextCombination of Thin Lenses in ContactCBSE PYQ

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A lens is a transparent medium bounded by two surfaces, with one or both surfaces being spherical. The focal length of a lens is determined by the radii of curvature of its two surfaces and the refractive index of its medium with respect to that of the surrounding medium. The power of a lens is reciprocal of its focal length. If a number of lenses are kept in contact, the power of the combination is the algebraic sum of the powers of the individual lenses.

CASE_STUDIESPower of a LensLens Maker's FormulaCombination of Thin Lenses in Contact

A lens is a transparent optical medium bounded by two surfaces; at least one of which should be spherical. Applying the formula of image formation by a single spherical surface successively at the two surfaces of a thin lens, a formula known as lens maker's formula and hence the basic lens formula can be obtained. The focal length (or power) of a lens depends on the radii of its surfaces and the refractive index of its material with respect to the surrounding medium. The refractive index of a material depends on the wavelength of light used. Combination of lenses helps us to obtain diverging or converging lenses of desired power and magnification.

CASE_STUDIESPower of a LensLens Maker's FormulaCombination of Thin Lenses in ContactLens Formula and Magnification with Sign ConventionDerivation of Lens Formula from Refraction at Spherical Surfaces

Describe a simple activity to observe diffraction pattern due to a single slit.

TextCombination of Thin Lenses in ContactDiffraction of Light at a Single Slit

The figure below shows an equiconvex lens (of refractive index 1.50) in contact with a liquid layer on top of a plane mirror. A small needle with its tip on the principal axis is moved along the axis until its inverted image is found at the position of the needle. The distance of the needle from the lens is measured to be 45.0 cm. When the liquid is removed and the experiment is repeated, the new distance is 30.0 cm. Find the refractive index of the liquid.

TextCombination of Thin Lenses in ContactDiffraction of Light at a Single SlitRefraction at Spherical Surfaces with Liquid Medium

In the given figure the radius of curvature of curved face in the plano-convex and the plano-concave lens is 15 cm each. The refractive index of the material of the lenses is 1.5. Find the final position of the image formed.

TextCombination of Thin Lenses in Contact

A lens is a portion of a transparent medium bounded by two surfaces and one of these surfaces is essentially spherical. It is used to converge or diverge the light incident on it. Power of a lens is the measure of its ability to converge or diverge the light incident on it. Power of a lens depends on the refractive index of the material of lens with respect to the surrounding medium and the radii of curvature of its two surfaces.

CASE_STUDIESSpherical Lenses: Convex and ConcavePower of a LensLens Maker's FormulaCombination of Thin Lenses in Contact