Optics Question 785

Question: A point object is located at a distance 15cm. from the pole of a concave mirror of focal length 10cm on its principal axis is moving with a velocity (8i^+11j^) cm/s and velocity of mirror is (4i^+2j^) cm/s as shown. If v is the velocity of image. Then find the value of |v| in (cm/s).

Options:

A) 20

B) 30

C) 10

D) 40

Show Answer

Answer:

Correct Answer: A

Solution:

[a] vobj,moier=4i^+9j^

dxdt=4,dydt=9,u=x

110=1V+1x;V=10xx10

vix=dVdt=(10x10)2(dxdt);vix=16

m=Vx=10x10=y10y

viy=(10x10)dydt;viy=18

vimage,mirror=16i^18j^;vimage=12i^16j^

|v|=20cm/s



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