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Question
Mon March 19, 2012 By:

# IN MIRRORS AND LENS PLEASE EXPLAIN, WHEN WE WILL TAKE FOCAL LENGTH AS NEGATIVE OR POSITIVE. PLEASE EXPLAIN BOTH IN LENS AND MIRRORS ABOUT OBJECT. IMAGE. FOCAL LENGTH. IMAGE IS REAL AND INVERTED OR IS VIRTUAL AND ERECT AND WHEN WE WILL TAKE THE SIGNS AS POSITIVE AND NEGATIVE.I AM NOT YET CLEAR IN THIS.

Wed March 21, 2012

## Generally, the New Cartesian Convention is used, according to which all distances are measured from the pole of the mirror. The distances measured in the same direction as the incident light (+ x axis) are taken to be positive, and those in the opposite direction as negative. The heights measured upwards (above the x-axis) and normal to the principal axis of the mirror are taken as positive, and the heights measured downwards as negative.

similarly in case of lens u can take the sign.
Related Questions
Wed February 15, 2017

# in an experiment the focal length of a convex lens a student obtained a sharp and inverted image of a distant tree on the screen behind the lens.she then removed the screen and looked through lens in the direction of the object .she will see a) an inverted image of the tree at the focus of the lens b)no image as the screen is removed c) a blurered image on the wall of laboratory d0 an erect image of the tree on the lens pls explain me the answer elaborately

Sun January 29, 2017

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