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Optics
22 Apr 2008 10:17:00 IST
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mohit jain
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22 Apr 2008 12:14:59 IST
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22 Apr 2008 12:50:59 IST
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for concave mirror
1/u + 1/v = 1/f
differentiating
-1/u^2du/dt - 1/v^2dv/dt = 0
=> velocity of image = - (v/u)^2velocity of object
Note:both are w.r.t to mirror
now to find v we use the mirror equation
1/v + 1/(-30) = 1/(-20)
=> 1/v = 1/30 - 1/20 = -1/60
so v = -60
so (v/u)^2 = (60/30)^2 = 4
so velocity of image w.r.t mirror = -4*2 = -8cm/sec
so velocity of image w.r.t ground = -8 - 2 = -10cm/sec
so velocity of image is 10cm/sec in the same direction as the velocity of mirror
22 Apr 2008 13:03:41 IST
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1/u + 1/v = 1/f
differentiating
-1/u^2du/dt - 1/v^2dv/dt = 0
=> velocity of image = - (v/u)^2velocity of object
now to find v we use the mirror equation
1/v + 1/(-30) = 1/(-20)
=> 1/v = 1/30 - 1/20 = -1/60
so v = -60
so (v/u)^2 = (60/30)^2 = 4
so velocity of image w.r.t mirror = -4*2 = -8cm/sec
so velocity of image w.r.t ground = -8 - 2 = -10cm/sec
so velocity of image is 10cm/sec in the same direction as the velocity of mirr
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