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Physics -- Optics
6.
An air bubble is inside water. The refractive index of water is
4/3. At what distance from the air bubble should a point object
be placed so as to form a real image at the same distance from the
bubble?
- A.2R
- B.3R
- C.4R
- D.The air bubble cannot form a real image
- Answer
- Report
Answer : [D]
7.
A spherical surface of radius of curvature R separates air from
glass (refractive index = 1.5). The centre of curvature is in the
glass. A point object P placed in air is found to form a real image
Q in the glass. The line PQ cuts the surface at a point O, and
PO = OQ. The distance PO is equal to
- A.5R
- B.3R
- C.2R
- D.1.5R
- Answer
- Report
Answer : [A]
8.
A point source of light at the surface of a sphere causes a parallel
beam of light to emerge from the opposite surface of the sphere.
The refractive index of the material of the sphere is
- A.1.5
- B.5/3
- C.2
- D.2.5
- Answer
- Report
Answer : [C]
9.
A thin lens of refractive index 1.5 has a focal length of 15 cm in
air. When the lens is placed in a medium of refractive index 4/3,
its focal length will become
- A.30 cm
- B.45 cm
- C.60 cm
- D.75 cm
- Answer
- Report
Answer : [C]
10.
A convex lens of focal length 40 cm, a concave lens of focal
length 40 cm and a concave lens of focal length 15 cm are placed
in contact. The power of this combination in dioptres is
- A.+1.5
- B.-1.5
- C.+6.67
- D.-6.67
- Answer
- Report
Answer : [D]
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