Magnification, power of lens, combination of thin lenses

In a certain camera, a combination of four similar thin convex lenses are arranged axially in contact. Then the power of the combination and the total magnification in comparison to the power (\(p\)) and magnification (\(m\)) for each lens will be, respectively -

In the figure shown here, what is the equivalent focal length of the combination of lenses (Assume that all layers are thin)?

Two thin lenses are of same focal lengths (\(f\)), but one is convex and the other one is concave. When they are placed in contact with each other, the equivalent focal length of the combination will be :

A biconvex lens has radii of curvature, 20 cm each. If the refractive index of the material of the lens is 1.5, the power of the lens is :

A convex lens 'A' of focal length 20 cm and a concave lens 'B' of focal length 5 cm are kept along the same axis with a distance 'd' between them. If a parallel beam of light falling on 'A' leaves 'B' as a parallel beam, then the distance 'd' in cm will be :

Two similar thin equi-convex 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 :

Match the corresponding entries of column 1 with column 2. [Where m is the magnification produced by the mirror]

Column 1: (A) \(m = -2\); (B) \(m = -\frac{1}{2}\); (C) \(m = +2\); (D) \(m = +\frac{1}{2}\)

Column 2: (a) Convex mirror; (b) Concave mirror; (c) Real image; (d) Virtual image

Two identical glass (\(\mu_g=3/2\)) equiconvex lenses of focal length \(f\) each are kept in contact. The space between the two lenses is filled with water (\(\mu_w=4/3\)). The focal length of the combination is

A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be