Question

WHICH DISTANCE IS CALLED OBJECT​

Answer 1

The distance from object to the lense or mirror is known as object distance.

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Answer 2

To find:

Which distance is called the object distance.

Solution:

In ray optics , the object distance

• in case of mirrors: is the distance from the pole of the mirror to the object.

• in case of lens: the distance from the optical centre (of lens) to the object.

Since the length is measured opposite to the direction of movement of light ray , the object distance is measured as negative.

In case of concave mirrors:

$\boxed{\setlength{\unitlength}{1cm}\begin{picture}(6,6)\put(1,3){\line(1,0){4}}\put(3,3){\oval(1,1)[r]}\put(1.5,3){\vector(0,1){0.25}}\put(3.5,2.25){\vector(-1,0){2}}\put(1.5,1.5){ \{-u\} }\end{picture}}$

In case of convex mirrors:

$\boxed{\setlength{\unitlength}{1cm}\begin{picture}(6,6)\put(1,3){\line(1,0){4}}\put(4,3){\oval(1,1)[l]}\put(1.5,3){\vector(0,1){0.25}}\put(3.5,2.25){\vector(-1,0){2}}\put(1.5,1.5){ \{-u\} }\end{picture}}$

In all cases of mirrors or lens , the object lens will be denoted as -u , this also helps in mathematical calculations.

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