# Ray Optics And Optical Instruments

15 Questions | Total Attempts: 1610  Settings  Time: 30 Minute

• 1.
The absolute refractive indices of water and glass are 1.3 and 1.5 respectively. The refractive index of water w.r.t. glass is
• A.
• B.
• C.
• D.

None of these

• 2.
The focal length of the lens is 50 cm; then its power is
• A.

+ 1 D

• B.

+ 2 D

• C.

– 2 D

• D.

– 1 D

• 3.
A convex mirror has a focal length f. A real object, placed at a distance f in front of it from the pole, produces an image at
• A.

F

• B.
• C.

2f

• D.

Infinity

• 4.
A convex lens of focal length x and a concave lens of focal length y are placed in contact. The focal length of the combination is
• A.

X + y

• B.

X - y

• C.
• D.
• 5.
A graph is plotted between the angle of incidence (i) and angle of reflection (r). The correct variation is shown by
• A.
• B.
• C.
• D.
• 6.
If a water drop is kept between two glass plates, then its surface is correctly shown by
• A.
• B.
• C.
• D.
• 7.
Figure shows three cases of a ray passing through a prism of refracting edge A. The case corresponding to minimum deviation is
• A.
• B.
• C.
• D.

None of these

• 8.
A glass prism of refractive index 1.5 is immersed in water (refractive index 4/3). A light beam incident normally on the face AB is totally reflected to reach the face BC if:
• A.

Sin C = 8/9

• B.

Sin C = 9/8

• C.

Sin C = 2/3

• D.

Sin C = 3/2

• 9.
In an experiment to find focal length of a concave mirror, a graph is drawn between the magnitude of u and v. The graph looks like:
• A.
• B.
• C.
• D.
• 10.
What should be the refractive index of a completely transparent medium for it to be visible in vacuum?
• A.

1

• B.

Less than 1

• C.

Greater than 1

• D.

None of the above

• 11.
Rainbow is formed due to combination of:
• A.

Refraction and absorption

• B.

Dispersion and foccusing

• C.

Refraction and scattering

• D.

Dispersion and total internal reflection

• 12.
The plane face of a plano-convex lens of focal length 20 cm is silvered as shown in Figure. What kind of a mirror will it behave?
• A.

Convex, f = 20 cm

• B.

Convex, f = 10 cm

• C.

Concave, f = 20 cm

• D.

Concave, f = 10 cm

• 13.
A telescope has an objective lens of 10 cm diameter and is situated at a distance of 1 km from two objects. The minimum distance between theses two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Ǻ is of order of:
• A.

5 mm

• B.

5 cm

• C.

2.5 m

• D.

5 m

• 14.
Focal length of a glass lens in air is 2 cm. Its focal length when immersed in water would be
• A.

4cm

• B.

6cm

• C.

8 cm

• D.

12 cm

• 15.
If a beam of light passes from air to glass, the speed of light
• A.

Decreases

• B.

Increases

• C.

Remains unchanged

• D.

It may increases or decrease depending upon the colour

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