10 Question answer on optical instruments
1. A person wants to see two pillars distance 11 km separately. The distance between the pillars be approximately
(a) 3.2 m
(b) 1 m
(c) 0.25 m
(d) 0.5 m
Ans: (a)
2. When the length of a microscope tube increases, its magnifying power
(a) Decreases
(b) Increases
(c) Does not change
(d) May increase or decrease depend on the observer and the place of observation?
Ans: (a)
3. The focal length of the objective of microscope is:
(a) Greater than the focal length of the eye piece
(b) Less than the focal length of the eye piece
(c) Equal to than the focal length of the eye piece
(d) Arbitrary
Ans: ( a)
4. A electron microscope is superior to an optical microscope in
(a) Having better resolving power
(b) Being easy to handle
(c) Low cost
(d) Quickness of observation
Ans: ( a)
5. The magnifying power of a simple microscope can be increased if we use eye piece of:
(a) Higher focal length
(b) Smaller focal length
(c) Larger diameter
(d) Smaller diameter
Ans: (b)
6. The resolving power of a telescope de[ends upon:
(a) The focal length of eye lens
(b) Focal length of objective lens
(c) The length of the telescope
(d) The diameter of the objective lens
Ans: (d)
7. An observer looks at a tree of height 15 metres with a telescope of magnifying power 10. To him, the tree appears
(a) 10 times taller
(b) 15 times taller
(c) 10 times nearer
(d) 15 times nearer
Ans: (c)
8. The focal length of the objective of a telescope is 60 cm. To obtain a magnification of 20, the focal length of the eye piece should be:
(a) 2 cm
(b) 3 cm
(c) 4 cm
(d) 5 cm
Ans: (b)
9. The focal length of a convex lens is 2.5 cm. its magnifying power will be?
(a) 25
(b) 52
(c) 11
(d) 1.1
Ans: (c)
10. A film projector magnifies a 100 sq cm film strip on a screen. If the linear magnification is 4, the area of magnified film on the screen is
(a) 1600 sq. cm
(b) 400 sq. cm
(c) 25 sq. cm
(d) 250 sq. cm
Ans: (a)