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A Numerical from Combination of thin lenses in contact

Two thin lenses of focal lengths f1=20cm and f2=60cm are placed in contact. find the focal length f3 of the combined lenses. find also the focal length f of a third lens placed in contact with these two that would result in overall focal length f11=-40cm. (Asked Young)
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Why the ray of light passing through optical center of a lens passes undeviated while when it passes through other points on the interface of the lens, it gets refracted?

Deviation is the change in direction of the ray while passing through the lens. The middle portion of the lens is comparatively flat and there is a point on the principal axis and inside the sphere through which all the undeviated rays pass. “Undeviated” doesn’t mean that there is no refraction. When we say that […]

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CBSE Question Paper 2007

SET -1 In a series LCR circuit, the voltages across an inductor, a capacitor and a resisitor are 30 V, 30V and 60 V respectively. What is the phase difference between the applied voltage and the current in the circuit? Ultraviolet radiations of different frequencies f1 and f2 are incident on two photosensitive materials having […]

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Commonly asked questions for AISSE (CLASS X CBSE) Physics (Set – 1)

(Collected from Previous Board Question Papers and CBSE Sample Papers andGuess Papers made by experienced teachers) Where does centre of curvature of a spherical mirror lie? Name two important properties of a magnet. How is 1 ohm related to ampere and volt? Draw neat ray diagrams to illustrate the formation of images due to a beam of light incident […]