# Competitive Exams: Physics MCQs (Practice_Test 34 of 35)

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Siphon will fail to work if

the densities of the liquid in the two vessels are equal

the level of the liquid in the two vessels are at the same height

both its limbs are of unequal length

the temperature of the liquids in the two vessels are the same

An object is placed between two plane minors inclined at an angle to each other. If the number of images formed is 7, then the angle of inclination is

15'

30'

45'

60'

A ray of light passes through a prism of angle 60'and refractive index 1.414. The angle of minimum deviation will be

15'

30'

45'

60'

In a prism, the dispersion is related to the wavelength l as

l − 1

l − 2

l − 3

l − 4

A light ray travels through media ‘A’ and ‘B’ having refractive indices of 4/3 and 3/2 respectively. If the thickness of the medium ‘A’ is 4 cm and that of ‘B’ is 6 cm, then the optical path length in the combined medial will be

7/3

12/3

37/3

43/3

Two lenses of equal power, but opposite sign, are mounted coaxiaily at a short distance apart from each other. Consider the following statements in this regard. If a parallel ray of light passed first through the positive lens and then through the negative lens, first through the negative lens and then through the positive lens, then the Which is correct?

equivalent power will be excessively positive in both the cases.

equivalent power will be negative in both the cases.

system will become a focal at two times the focal length of each lens.

Of these statements

1 alone is correct

2 alone is correct

1 and 3 are correct

2 and 3 are correct

Two lenses of power + 5 dioptres each and separated by a distance ‘d’ will become afocasys when the value of ‘d’ is

zero

10 cm

25 cm

40 cm

A drop of water is placed between two glass plates (assume that the glass plates are of negligible weight) on a table. The drop of water flattens into a film of thickness d = 10 − 6m and area 8 × 10 − 4m2. If the surface tension of water is 70 × 10 − 3Nm-1, then the force required to lift the top plate (clearly separating it from the bottom plate) will be

224 N

112 N

56 N

2.24 × 10 − 12 N

Two lenses of dispersive powers of 0.01 and 0.02 can form an achromatic doublet only when the ratio of their focal lengths is

(2) ½ 1

2: 1

-2: 1

1: 2

Match List I (Types of glasses used in lens making) with List II (The index of refraction at X = 587.6 mm) and select the correct answer

List-I List-II Fused silica

Dense flint

Borosilicate crown

Light barium crown

1.517

1.572

1.458

1.805

- A
- B
- C
- D

- 3
- 4
- 1
- 2

- 3
- 4
- 2
- 1

- 4
- 3
- 1
- 2

- 4
- 3
- 2
- 1

A Cassegranian telescope has a primary of 40 cm radius of curvature and a secondary of 10 cm radius of curvature and the mirror separation of 15 cm. The equivalent power of the system (in dioptres) is

zero

0.5

1.0

1.5

If the focal length of the more convergent lens of a Huygen's eyepiece is 0.5 cm, then the focal length of the eyepiece will be

0.5 cm

0.75 cm

1.50 cm

2.0 cm

A microscope has an objective of 3mm focal length and eyepiece of 30mm focal length and the distance between them is 157mm. The magnification is

90 x

150 x

180 x

35 x

The crystalline lens of the human eye has a refractive index of 1.41 at its centre and 1.38 at the periphery. A small slice of 0.01 cm is cut out and seen through a Mach Zehdner interferometer with light of 600 nm. The distortion produced in the fringes is

5

10

0.5

1.0

Two monochromatic light waves of amplitudes A and 2 A interfering at a point have a phase difference of 60' The intensity at that point will be proportional to

3A2

5A2

7A2

9A2