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CBSE - X - Physics - Light - Reflection and Refraction

Hellow Sir, I am having a great difficulty in solving the Numericals just because I cannot guess what is u, what is v,h1,h2 and all that. Please help to crack numericals at ease. I will be Highly thankful to you.

Asked by SBMDXT 5th February 2011, 4:30 PM
Answered by Expert


Dear student
I will suggest that you read the question twice, try to interpret it and identify the given quantities as well as the quantities to be found.
Here, f = 25cm, u = ?, v= 75cm.
Now, 1/f = 1/v - 1/u
or, 1/u = 1/v - 1/f = 1/75 - 1/25 = -2/75 cm
or, u = -37.5 cm
hence the object is placed 37.5 cm to the left of the lens i.e. in the direction opposite to that of incident rays.
Also, m = v/u = I /O
or, I = (v/u) x (O) (to calculate size of the image , size of the object should be known, sign of the image tells about the nature of the image)
Hope this helps.
Answered by Expert 7th February 2011, 2:16 PM

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