Q. 1.
A telescope has an objective of focal length 50 cm and eyepiece of
focal length 5 cm .The least distance of distinct vision is 25cm.The
telescope is focused for distinct vision on a scale 200 cm away from the
object. Calculate (a) the separation between the objective and eyepiece
and (b) the magnification produced. (70.83 cm, -2)
Q. 2.
A telescope objective of focal length 1 m forms a real image of the
moon 0.92 cm in diameter. Calculate the diameter of the moon taking its
mean distance from the earth to be 38x104 km. (3.5 x106 m)
Q. 3.
An angular magnification of 30X is desired using an objective of focal
length 1.25 cm and an eyepiece of focal length 5 cm. How will you set up
the compound microscope? (L=11.67cm.)
Q. 4.
A compound microscope is used to enlarge an object kept at a distance
of 0.30 m from its objective, which consists of several convex lenses
and has focal length 0.02 m. If a lens of focal length 0.1 m is removed
from the objective, find out the distance by which the eyepiece of the
microscope must be moved to refocus the image? (9cm.)
Q. 5.
An amateur astronomer wishes to estimate roughly the size of the sun
using his crude telescope consisting of an objective lens of focal
length 200 cm and eyepiece of focal length 10 cm. By adjusting the
distance of the eyepiece from the objective, he obtains an image of the
sun on a screen 40 cm. behind the eyepiece. The diameter of the sun’s
image is measured to be 6 cm. What is his estimate of the sun’s size,
given that average earth – sun distance is 1.5x1011 m. (1.5 x 109 m)
Q. 6.
A 35 mm slide with a 24 mm x 36 mm picture is projected on a screen
placed 12 m from the slide. The image of the slide picture on the screen
measures1.0mx1.5 m. Determine the location of the projection lens and
its focal length? (28.1cm, 27.5 cm)
Q. 7.
An eyepiece of a telescope consists of two plano convex lenses L1 and
L2 each of focal length f separated by a distance of 2ƒ/3. Where should
L1 be placed relative to focus of the objective lens of telescope, so
that the final image through L2 is seen at infinity? (ƒ/4)
Q. 8.
A telescope has a objective of diameter 60 cm. The focal lengths of the
objective and eyepiece are 2 m and 1.0 cm respectively. The telescope
is directed to view two distant point sources of light (e.g. two stars
of a binary). The sources are roughly at the same distance ( 104 light
years) along the line of sight, but separated transverse to the line of
sight by a distance of 1010 m. Will the telescope resolve the two
objects? (Take, λ =6x10-7 m for mean yellow color.) (No)
Q. 9.
The separation between the eyepiece (of focal length 0.3 m) and
objective (of focal length 0.4 m) of a microscope is 0.2 m. The eyepiece
and the objective are to be interchanged such that the angular
magnification of the instrument remains the same. What is the new
separation between the lenses? Hint: use, m = (0.3m)
Q. 10.
The image of the moon is focused by a converging lens of focal length
50 cm on a plane screen. The image is seen by an unaided eye from a
distance of 25 cm. Find the angular magnification achieved due to the
converging lens? (- 2)
Q. 11.
The objective of telescope A has a diameter 3 times that of the
objective of telescope B. How much greater amount of light is gathered
by A compared to B? Show that range of A is three times the range of B?
[Hint: Intensity α ] (9 times)
Q. 12.
The diameter of sun is several hundred times bigger than the moon,
still at the time of solar eclipse, the moon covers the entire sun. How?
Q. 13. How does magnifying power change with change in length of tube of a given telescope and microscope each?
Q. 14.
Distinguish between linear magnification and angular magnification.
When are these two magnifications equal? 15. When viewing through a
compound microscope, our eye should be positioned not on the eyepiece,
but a short distance away from it. Why? How much should be that short
distance between the eye and the eyepiece?
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