KCET · Physics · Ray Optics
Focal length of a convex lens is \( 20 \mathrm{~cm} \) and its (RI) is \( 1.5 \). It produces an erect, enlarged image
if the distance of the object from the lens is
- A \( 40 \mathrm{~cm} \)
- B \( 30 \mathrm{~cm} \)
- C \( 15 \mathrm{~cm} \)
- D \( 20 \mathrm{~cm} \)
Answer & Solution
Correct Answer
(C) \( 15 \mathrm{~cm} \)
Step-by-step Solution
Detailed explanation
Given, focal length \( f=20 \mathrm{~cm} \); refractive index \( =1.5 \) Image produced is erect and enlarged.
We know, when the object is placed between focal length and optical center of the lens, image, formed on same side of
lens and is enlarged, virtual and erect.
Thus, the distance of object from lens should be less than the focal length, that is, \( 15 \mathrm{~cm} \)
We know, when the object is placed between focal length and optical center of the lens, image, formed on same side of
lens and is enlarged, virtual and erect.
Thus, the distance of object from lens should be less than the focal length, that is, \( 15 \mathrm{~cm} \)
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