Geometrical OpticsHard
Question
An eye specialist prescribes spectacles having combination of convex lens of focal length 0 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination is diopters is
Options
A.+ 1.5
B.- 1.5
C.+ 6.67
D.- 6.67
Solution
The focal length of combination is given by
or
cm = - 
∴ Power of the combination in dioptres,
P = - 
= - 1.5
or
cm = - ∴ Power of the combination in dioptres,
P = -
= - 1.5
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