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| Relation between Focal Length and Radius of Curvature in Spherical Mirrors |
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| Consider a ray of light AB, parallel to the principal axis, incident on a spherical mirror at point B. The normal to the surface at point B is CB and CP = CB = R, is the radius of curvature. The ray AB, after reflection from mirror will pass through F (concave mirror) or will appear to diverge from F (convex mirror) and obeys law of reflection, i.e., i = r. |
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| From the geometry of the figure, |
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| If the aperture of the mirror is small, B lies close to P, \ BF = PF |
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| or FC = FP = PF |
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| or PC = PF + FC = PF + PF |
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| or R = 2 PF = 2f |
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| Similar relation holds for convex mirror also. In deriving this relation, we have assumed that the aperture of the mirror is small. |
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| Object at Infinity |
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| Object at Infinity |
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| Object at 2F or C |
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| Object at 2F or C |
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| Object between C and F |
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| Object at F |
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| Object beyond C |
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| Object between F and P |
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| Table depicting the position and nature of the object and image |
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| Image for a convex mirror is small, erect and diminished. |
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| Real images form on the side of a mirror where the object is and the virtual images for on the opposite side. |
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