Question 329: Ray Optics

Question

When an object is kept at a distance of 30 cm from a concave mirror, the image is formed at a
distance of 10 cm from the mirror. If the object is moved with a speed of 9 cms–1, the speed
(in cms–1) with which image moves at that instant is ____.

Accepted Answer

V
I
= Velocity of image with respect to mirror
V
0
= Velocity of object with respect to mirror
$$|\overrightarrow {{V_I}}|  =  |- {{{v^2}} \over {{u^2}}}\overrightarrow {{V_0}} |$$
$$ = | - {{10 	imes 10} \over {30 	imes 30}} 	imes 9|$$
$$ = 1$$ cm/s

Ray Optics

When an object is kept at a distance of 30 cm from a concave mirror, the image is formed at a distance of 10 cm from the mirror. If the object is moved with a speed of 9 cms–1, the speed (in cms–1) with which image moves at that instant is ____.

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