THIN LENS + HCV QUESTIONS

Thin Lens Formula

A thin convex lens of focal length 10 cm and a thin concave lens of focal length 26.2 cm are in contact. The combination acts as

A beam of parallel rays is brought to focus by a planoconvex. A thin Concave lens of the same focal length is joined to the first lens. The effect of this is

A spherical mirror and a thin spherical lens have each a focal length of - 15 cm . The mirror and lens are likely to be

A thin lens has a focal length of - 25 cm . What is the power of the lens? It is convex or concave ?