MHT CET · Physics · Ray Optics
An optician makes spectacles having a combination of a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm . The power of this combination of lenses in dioptre is
- A -6.67
- B -1.5
- C 6.67
- D 1.5
Answer & Solution
Correct Answer
(B) -1.5
Step-by-step Solution
Detailed explanation
\(P=\frac{1}{f}\)
For combination of lenses,
\(\mathrm{P}=\mathrm{P}_1+\mathrm{P}_2\)
Given: \(\mathrm{P}_1=2.5 \mathrm{D}\) and \(\mathrm{P}_2=-4 \mathrm{D}\)
\(\therefore \quad P=-1.5 D\)
For combination of lenses,
\(\mathrm{P}=\mathrm{P}_1+\mathrm{P}_2\)
Given: \(\mathrm{P}_1=2.5 \mathrm{D}\) and \(\mathrm{P}_2=-4 \mathrm{D}\)
\(\therefore \quad P=-1.5 D\)
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