# lens maker formula for concave lens

If the distance of the object is 30cm from the lens, find the position, nature and size of the image. following assumption are considered while deriving lens maker's formula for concave lens a) only point object is taken b) the aperature of the lens is small So, focal length of a lens increases when it is immersed in water. Note that the formula is true for a concave lens also. Derivation of lens Makers Formula from AB INITIO CONCAVE LENS - Physics - Ray Optics And Optical Instruments Consider an object O placed on the principal axis of the thin lens. Lens maker's Formula: It is a relation that connects the focal length of a lens to radii of curvature of the two surfaces of the lens and the refractive index of the material of the lens. Here µ is refractive index of lens material to the medium outside. Place a thin lens (which is made of one convex surface and one concave surface) between two refractive indices. This causes light that enters the lens to spread out, or diverge. In that case R 1 is negative, R 2 positive and therefore, f is negative. It is useful to design lenses of desired focal length using surfaces of suitable radii of curvature. Let n a be the refractive index of one medium and and n b be the refractive index of second medium. 2. Using lens formula the equation for magnification can also be obtained as . Also find its magnification. Lens maker s formula and lens formula . Applicable for both the convex and concave lenses, the lens formula is given as: 1/v - 1/u = 1/f Where, v = Distance of image formed from the optical center of the lens. 3. Q1. m = h 2 /h 1 = v//u = (f-v)/f = f/(f+u) This equation is valid for both convex and concave lenses and for real and virtual images. Concave Lens: A concave lens is any lens that has an inward curve in the middle. This is lens maker’s formula. A 4cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20cm. Consider two thin convex lenses L 1 and L 2 of focal length f 1 and F 2 placed coaxially in contact with each other. As per optical physics, lens formula relates the distance of an object (u), the distance of an image (v), and the focal length (f) of the lens. Combination of Thin Lenses. In the case of a concave lens, it is always positive. Lens maker’s formula - Equation 1. Equation (5) is known as Lens Maker’s Formula. In other words, the edges of the lens are thicker than the middle.

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