Question 308: Ray Optics

Question

An object is placed at a distance of 40 cm
from a concave mirror of focal length 15 cm.
If the object is displaced through a distance
of 20 cm towards the mirror, the displacement
of the image will be

Accepted Answer

Using mirror formula,
$${1 \over f} = {1 \over {{v_1}}} + {1 \over {{u_1}}}$$
$${1 \over { - 15}} = {1 \over {{v_1}}} - {1 \over {40}}$$
$$ \Rightarrow $$ v
1
= Ã¢ÂÂ24 cm
When object is displaced by 20 cm towards
mirror.
Here u
2
= Ã¢ÂÂ20
So, $${1 \over f} = {1 \over {{v_2}}} + {1 \over {{u_2}}}$$
$${1 \over { - 15}} = {1 \over {{v_2}}} - {1 \over {20}}$$
$$ \Rightarrow $$ v
2
= -60 cm
So, the image will be shift away from mirror by
(60 Ã¢ÂÂ 24) cm = 36 cm.

Answer

30 cm away from the mirror

Answer

36 cm away from the mirror

Answer

30 cm towards the mirror

Answer

36 cm towards the mirror

Ray Optics

An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be

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