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

144
PROBLEMS
.9'
Fig. 247
length of f = 21 em will the image of the lamp filament be
sharp?
Can an image be obtained if the focal length is I' = 26 em?
717. A thin convergent lens produces the image of a certain
object on a screen. The height of the image is hi. Without
changing the distance between the object and the screen, the
lens is shifted, and it is found that the height of the second
sharp image is h 2
• Determine the height of the object H.
718. What is the radius R of a concave spherical mirror at
a distance of a = 2 metres from the face of a man if he sees
in it his image that is one and a half times greater than on
a fiat mirror placed at the same distance from the face?
719. Figure 245 shows ray AB that has passed through a
divergent lens. Construct the path of the ray up to the lens
if the position of its foci F is known.
720. Figure 246 shows 8 luminescent point and its image
produced by a lens with an optical axis NIN 2. Find the position
of the lens and its foci.
721. Find by construction the optical centre of a lens and
its main foci on the given optical axis N IN 2 if the positions
of the source S and the image S' are known (Fig. 247).
722. The position of the optical axis N IN2' the path of ray
AB incident upon a lens and the refracted ray Be are known
(Fig. 248). Find by construction the position of the main foci
of the lens.
723. A convergent lens produces the image of a source at
point S' on the main optical axis. The positions of the centre
of the lens 0 and its foci F are known, and OF < OS'. Find
by construction the position of source S.
A~t'
B