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A beaker having water of refractive index of 4/3 water is filled upto 16 cm in it. As shown in figure, a concave mirror is kept 3 cm above the surface of water. If the object is place at the bottom of beaker and its image is ob tained from this mirror at 7 cm below the surface of water, then what will be the focal length of this concave mirror ? |
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Answer» 4 cm `implies h_i=h_0xx3/4` `=(16xx3)/(4)`=12 cm `therefore` Object distance from concave MIRROR =u=12+3=15 cm  Image distance =v=7+3=10 cm `therefore 1/f=1/u+1/v` `implies1/f=(1)/(-15)+(1)/(-10)+(2+3)/(-30)=(5)/(-30)=-1/6` Thus, focal LENGTH =f=6 cm |
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