Draw the ray diagram. Dioptre formula is used to calculate the optical power of a lens or curved mirror. << << /Width 71 /BitsPerComponent 8 power of +3.00 Lens surface power can be found with the index of refraction and radius of curvature. An object 5 cm high is held 25 cm away from a converging lens of focal length 20 cm. New Cartesian Sign Conventions for refraction of light, Rules for Obtaining Images by Spherical Lenses. A concave lens of focal length 15 cm forms an image 10 cm from the lens. 2 0 obj /ColorSpace/DeviceRGB How far is the object placed from the lens? A lens is said to be of greater power if it diverges or converges a beam of light more strongly by focusing them closer to the optical centre. Draw the ray diagram and find the position, size and nature of the image formed. >> Draw the ray diagram and find the position, size and nature of the image formed. The dioptre is the unit for a measure of the refractive index of a lens. /Filter/FlateDecode So for example, if a lens has a focal length = 100 cm = 1 m Power would be= 1 D Test Your Understanding and Answer These Questions: A lens formula may be defined as the formula which gives the relationship between the distance of image (v), distance of object (u), and the focal length (f) of the lens. An object 5 cm high is held 25 cm away from a converging lens of focal length 20 cm. endobj /Subtype/Image /Type/ExtGState X�ݙ�WSI���9g��M� ;��[�A��M�idIBd �]HXe�ЄfiY�ɞ0��h@@�"3���8������ｷ�n�0GKh#�L}�Lk��9Qł6Y͞�bNV0&*�匉J��^+Y���� �&���B�H�͎�b�&^[��/-|������O�^��3h��9��2��r�2���f6��zNR��l��Q�An����{�M�\6�ͥu�}�ѷ��y¸����A�->�~����l�h���/.fb3�=��$�.�����E|>��sI�2>K9=�A���VEI/�Kt�qz''Ť��J����-&��"���$�T�S����M��jm卟��D���[���4���3!��b�)��(a��Z���s�!P%9��8T��A-tS. /OP true A lens formula may be defined as the formula which gives the relationship between the distance of image (v), distance of object (u), and the focal length (f) of the lens. Lens Formula and Magnification - Lens Power Lenses, both converging and diverging, are the marvels of optical physics that use the ability of these media to refract, reflect, or bend light rays. %���� /Type/ExtGState endobj The lens formula is applicable both in convex lenses and concave lenses. The formula for surface power is Ds = (u-1)/r, where u is the index of refraction and r the radius of curvature in meters. << %PDF-1.4 Formula of power of a lens is : Here P(Power) is expressed in ‘D’(Dioptre) and Focal length is expressed in ‘m’(meter). Therefore, the power of this particular lens if 5D. Power of Lens … In other words, a lens of small focal length is said to have greater power. 1 0 obj The power of a lens is specified as the inverse of the focal length in meters, or D =\[\frac{1}{F}\], where D is the power in dioptres. /Height 46 Is lens formula applicable only for convex lens? >> For example, if the focal length of a lens is 20 cm, converting this to meters, we get 0.2 m To find the power of this lens, take the reciprocal of 0.2, and we get 5. /Length 2355 /OP false stream It may be written as: Where, v = Distance of image from optical centre of lens u = Distance of object from optical centre of lens and f = Focal length of lens. /OPM 1 In general, the lenses come in two shapes: convex (curved outward) and concave (curved inward). The power of a lens is defined as the ability of the lens to converge or diverge a beam of light falling on it. /Type/XObject >> A concave lens of focal length 15 cm forms an image 10 cm from the lens. Define lens formula. 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