Aptitude Test Problems in Physics Science for Everyone by S Krotov ( PDFDrive.com )

(^300) Aptitude Test Problems in Physics
is filled with water:
— h) nw 2hno = nw ll + h.
Here fl is the focal length of the objective lens in
the presence of water. Substituting the values of h
and + riA.,- fi + //(2/ 1 ), we obtain
2
2 f
r2
4
ri
i
nw
21
[(n
g
—1)+ (no — nw )].
Hence
Row
11 (n0-1)±(no—nw) •
When the telescope does not contain water, the
focal length of the objective lens is
AO) Ri^
2 (ngi-1) •
Therefore,
h=1(i0) (^) ogi_1)_F(ngi—nw)
2 (no —1) nw
A similar calculation for the focal lengths f 2
(with water) and fp (without water) of the eye-
piece lens gives the following result:
2 (ngi —1)
fs=f4°) (no--1)+(no
nw
nw)
Therefore,
2 (no-
L=" i2= UP + ) (^) (no-1)±(no1) (^) —nw) •
Since PIV + 1W = Lo, the required distance be-
tween the objective and the eyepiece is
L=L° 2ng1 nw —
30 cm.
2 (no —1) nw^