COMEDK Exam 2019 Solved Paper

Resultant focal length (f) of the given combination is 0.2m.
Refractive index of the material, µ=1.5
From the lens Maker formula, we get
‌

1

f

=(µ−1)(‌

1

R1

−‌

1

R2

)where, R1 is the radius of curvature of convex surface and R2 is the radius of curvature of plane surface (R2=∞).
Hence,
‌

1

f

‌=(15−1)(‌

1

R1

−‌

1

∞

)
⇒‌‌‌

1

0.2

‌=(0.5)(‌

1

R1

)
⇒‌‌R1‌=0.5×0.2=0.1m