Problem regarding concave mirror..

1. The problem statement, all variables and given/known data

A point object at 15 cm from a concave mirror of radius of curvature 20 cm is made to oscillate along principal axis with amplitude 2 mm. Find the amplitude of its image.

2. Relevant equations

Mirror formula :

1/v + 1/u = 1/f

Here u=-15 cm , f=-10

Differentiating above formula

dv/dt = -m2 du/dt

Where m= transverse magnification=-v/u

3. The attempt at a solution

Ok I don’t know if it’s SHM or just another sort of oscillatory motion. Had it been SHM I would have solved it by putting maximum velocity = amplitude times angular frequency.

SHM: Simple harmonic motion.

My attempt :

1/v + 1/u = 1/f
u=-15 cm , f=-10

Thus m=-v/u = -2


dv/dt = -4 du/dt

Now ?

Please help !!

Thanks in advance….


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