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Eperiment-04
28
28
29
PRECAUTIONS
1. The axis of the telescope should be horizontal and at right angle to the
plane of the metallic strip.
Experiment-04
4.
Ans. To see two objects as separate is called resolution, or
2. The width, aperture, and the distance between the objects should be
measured carefully.
3. The distance D should be measured from the slit of the telescope to the
stripped glass.
resolution =
learning about the resolving power of optical devices in general and telescope
in specific.
CRITICISM
1
resolving power
5
What do you mean by resolving limit ?
Ans. (See question 4) Minimum angle subtended by the two objects when their
PRACTICAL APPLICATIONs
Telescope is a device to observe distant objects. Experiment helps us
29
What is meant by resolution ?
images are seen as just separated is called resolution limit.
6
What is the resolution limit of a normal eye?
Ans. The resolution limit of a normal eye is about one minute.
7.
Why do you get the theoretical value different from the practical one?
Ans.
3.
This is because there is enough arbitrariness about the resolution limit as
observed by different eyes. This may also be due to the telescope not being
focussed well on the object.
Define magnifying power of the telescope ?
Ans. It is defined as the ratio of angle subtended at the eye by the final image
to the angle subtended by the object at the eye when viewed the object
VVA-VOCE
1.
What is meant by resolving power of a telescope ?
Ans. Resolving power of a telescope is defined as the reciprocal of least angle sub
tended by two closely objects at the objective of the telescope when the
images of those objects are seen just separate at its focal plane.
2.
On what factors does the resolving power of telescope depend ?
Ans. The resolving power of the telescopedepends on the wavelength of light
used and the aperture of the objective.
3.
How does the resolving power of telescope depend on the aperture of
the objective ?
Ans. Larger the aperture of the objective, higher is the resolving power of the
telescope.
directly.
9.
On what factors does the magnifying power of telescope
depend ?
Ans. The magnifying power of the telescope depends upon the focal lengths F and f
of the objective and the eyelens respectively as for an unaccommodated eye.
10. Is the resolving power of the telescope different
from magnifying power ?
Ans. Yes, magnifying power of the telescope measures the ability to increase the
angle subtended by the object, whereas the resolving power measures the
ability to see images of two close objects clearly as separate.
11
If you get a bright central spot in reflected light, can you even then,
determined the wavelength of light ?
Ans. The formula for the determination of wave length of light is
independent of
the order of the ring at the centre. Hence measurements can be
made with
that also without any error coming in.
30
12.
30
Experiment-04
If the aperture diameter of the telescope is given to be 100 inches, how
do we determine its limit of resolution?
Ans. Apply formula for limit of resolution:
dÇ =
122
122 x 6x 10x180 x 60 x 60
100x 2.54 x3.14
Sec.
13.
What is the resolution limit of your telescope?
Ans.
Explore yourself.
14.
What is the difference between magnification and resolution?
Ans.
(a)
(a)"
M
(©)
(d)
() Cases of increasing magnificat
ion but decline in resolution.
(a)
(b)
(b)
(i)Distinction between magni
fication and resolution.
Fig. (b) has greater magnification
but bad resolution.
(iii) Spectrum in (a) has magni
fication but less resolution than
that in (b)
Figure: 4.2
Magnification means enlargement of the image observed by an optical
instrunent.
Resolution which is reciprocal of the resolving power of an optical
instrument, is the ability of that instrument to see two near by objects distinctly.
Resolution depends on smallness of the "spread of images. Smaller the
Spread, better the resolution. The spread is governed by width of 'apertures' relative
to A.. Magnification, in contrast, is related to the separation of centres of images.
Larger the separation better the magnification.