Q2 of 84 Page 324

A convex mirror of focal length f forms an image of the size of the object. The distance of the object from the mirror is

According to the question


Magnification (m) = (image is of the size of object).


Focal length = f (positive for convex mirror).


Object distance = -u.


Now By formula.



⇒


⇒ f + u = nf


⇒ u = nf – f


⇒ u = (n-1)f.


Therefore the object distance from the mirror is (n-1)f. Hence the option C is correct.

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Mr. Raghav, grade 6 teacher find that his students do not draw when he draws on the board. Every time he had to turn towards them to see whether they draw and label the diagrams. Arav, one of his student fixed two big convex mirrors at the two sides of the black board. With this Mr. Raghav was able to draw and also supervise his students through the mirror. All the students started doing their work property.

(i) Which characteristics of convex lens, let Mr. Raghav to do both his job at the same time?


(ii) What value did Arav and Mr. Raghav show?

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An object is placed at the centre of curvature of a concave mirror. The distance between its image and the pole is