An object is placed at a distance of 40 cm from a
concave mirror of focal length 15 cm. If the obiect
is displaced through a distance of 20 cm towards
the mirror, the displacement of the image will be:-
(1) 30 cm away from the mirror
(2) 36 cm away from the mirror
(3) 30 cm towards the mirror
(4) 36 cm towards the mirror
Answers
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Answer:
36 cm away from mirror.
Explanation:
It just needs to be done as two separate calculations then the difference of the two answers is found.
In the initial setup, the object distance is 40 cm, which gives 24 cm image distance given the focal length of 15 cm.
equation: 1/15= 1/40 + 1 ...(i)
The second equation changes object distance to 20 cm (40–20), which results in 60 cm as the image distance.
equation: 1/15= 1/20 + 1 ...(ii)
∴ The difference between 60 and 24 is 36 cm (in the direction away from mirror).
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