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An object is placed at 20 cm in front of a concave mirror produces three times magnificed real image. What is the focal length of the concave mirror ? |
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Answer» 15 cm Linear magnification `m = (f)/(f - U)` Given, object displaced u = - 20 cm `(therfore "all REAL image are inverted")` So, "" `-3 = (f)/(f - (-20))` `rArr "" -3 = (f)/(f + 20) rArr - 3F - 60 = f` `4f = - 60 rArr f = - (60)/(4) = - 15 cm` Since, mirror is concave f = - 15 cm. |
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