f11=21×182
f21=−18(μ1−1)
When μ1 is filled between lens and mirror,
P=182−182(μ1−1)=182−2μ1+2
⇒Fm=−(2−μ118)
2=6−3μ1
3μ1=4
μ1=34
JEE Main 2019 — Physics Optics
2019mcqhard
A thin convex lens L (refractive index =1.5 ) is placed on a plane mirror M. When a pin is placed at A, such that OA=18cm, its real inverted image is formed at A itself, as shown in figure. When liquid of refractive index μl is put between the lens and the mirror, the pin has to be moved to A′, such that OA′=27cm, to get its inverted real image at A′ itself. The value of μl will be
Official previous-year question
Held on 9 Apr 2019 · Verified 6 Jul 2026.
Options
- A
34
- B
3
- C
23
- D
2
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