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Two object A and B when placed in turns infront of a concave mirror, give images of equal size. The focal length of the concave mirror is 7.5cm and size of object A is three times the size of object B from the mirror , if A is placed 30cm from the mirror. |
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Answer» `18cm` Here `l_(A)=O_(A)` and `O_(A)=3O_(B)` `(m_(A))/(m_(B))=(l_(A))/(O_(A))XX(O_(B))/(l_(B))=(l_(A))/(O_(A))=1/3` also, `m_(A)=f/(f-u_(A))` and `m_(B)=f/(f-u_(B))` ` (m_(A))/(m_(B))=((f-u_(B))/(f-u_(A)))` `1/3=(-7.5-u_(B))/(-7.5-(-30))` `u_(B)=-15cm` |
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