(i) What is the focal length (in air) of a thin lens having refractive index 1.50, and radii of
curvature R1 = – 0.50 m and R2 = – 0.60 m? Is this lens converging or diverging?
(ii) Now suppose that a lens, with the same radii of curvature as in part (i), is hollow (i.e. filled
with air) and immersed in an oil bath. The oil and the glass forming the lens boundaries each have
a refractive index, n = 1.50. What is the focal length of this lens? Is this lens converging or
diverging (for your own knowledge, think about how you can rationalize your answer)?

Question

(i) What is the focal length (in air) of a thin lens having refractive index 1.50, and radii of 
curvature R1 = – 0.50 m and R2 = – 0.60 m? Is this lens converging or diverging? 
(ii) Now suppose that a lens, with the same radii of curvature as in part (i), is hollow (i.e. filled 
with air) and immersed in an oil bath. The oil and the glass forming the lens boundaries each have 
a refractive index, n = 1.50. What is the focal length of this lens? Is this lens converging or 
diverging (for your own knowledge, think about how you can rationalize your answer)?