Two thin equiconvex lenses each of focal length 0.2 m are placed coaxially with their optic centres 0.5m apart. Then find the focal length of the combination.

Two thin equiconvex lenses each of focal length 0.2 m are placed coaxially with their optic centres 0.5 m apart.Then the foacla length of the combination is

Two thin equiconvex lenses each of focal length 0.2 m are placed coaxially with their optic centres 0.5m apart. Then focal length of combination is

Two similar thin equiconvex lenses, of focal length f each, are kept coaxially in contact with each other such that the focal length of the combination is F_1 . When the space between the two lenses is filled with glycerin (which has the same refractive index (mu = 1.5) as that of glass) then the equivalent focal length is f_2 . The ratio F_1 : F_2 will be:

When two thin lenses are kept in contanct, the focal length of the combination is

When two thin lenses are kept in contanct, the focal length of the combination is

Two convex lenses of focal lengths 25 cm and 15 cm are placed in contact with each other. Find the focal length of combination.

Two thin plano-convex lenses each of focal length f are placed as shown in the figure . The ratio of their effective focal lengths in the three cases is

Two concave lenses, eacb of focal length 30 cm are placed in contact with each other. Find the power of the combination.