1 )
An object is placed at a distance of f/2
from a convex lens . The image will be : -
Solution : -
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2 )
If tube length of astronomical telescope is 105 cm and magnifying power is 20
for normal setting , calculate the focal length of objective ?
Solution
: -
L = 105 cm , m = 20
, Fo = ?
So , we have formula : -
M = Fo / Fe
,
So , it will become : -
Fo = 20 Fe .
Now we use 2nd formula : -
L = Fo + Fe ,
105 = Fe + 20 Fe
,
So , Fe = 5 cm .
So , now we will find Fo by same formula : -
L = Fo + Fe
,
105 = Fo + 5
,
Fo = 100 cm .
So ,
answers are Fo = 100 cm and Fe
= 5 cm .
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