Bukhovtsev-et-al-Problems-in-Elementary-Physics

146 PROBLEMS
a point source arranged on the optical axis? Disregard the reflec-·
tion of light on the boundary between layers.
729. The visible dimensions of the disks of the Sun and the
Moon at the horizon seem magnified as compared with their
visible dimensions ·at the zenith. How can it be proved experimentally
with the aid of a lens that this magnification is
apparent?
5-4. Optical Systems and Devices
730. A source of light is located at double focal length from
a convergent lens. The focal length of the lens is f = 30 em.
At what distance from the lens should a flat mirror be placed
so that the rays reflected from the mirror are parallel after
passing through the lens for the second time?
731. A parallel beam of rays is incident on a convergent
lens with a focal length of 40 em. Where should a divergent
lens with a focal length of 15 em be placed for the beam of
rays to remain parallel after passing through the two lenses?
732. An object is at a distance of 40 em from a convex
spherical mirror with a radius of curvature of 20 em. At what
distance from the object should a steel plate be placed for the
image of the object in the spherical mirror and the plate to
be in one plane?
733. At what distance from a convexo-convex lens with a
focal length of f = 1 metre should a concave spherical mirror
with a radius of curvature of R= 1 metre be placed for a beam
incident on the lens parallel to the major optical axis of the
system to leave the lens, remaining parallel to the optical axis,
after being reflected from the mirror? Find the image of the
object produced by the given optical system.
734. An optical system consists of two convergent lenses with
focal lengths '1 = 20 em and t, == 10 ern. The distance between
the lenses is d = 30 em. An object is placed at a distance of
at = 30 cm from the first lens. At what distance from the second
lens will the image be obtained?
735. Determine the focal length of an optical system consisting
of two thin lenses: a divergent one with a focal length t.
and a convergent one with a focal length {20 The lenses are
fitted tightly against each other, so that the distance between
them can be neglected. The optical axes of the lenses coincide.