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CBSE

Subject

Physics

NEET Physics : Ray Optics and Optical Instruments

Multiple Choice Questions

151.

The magnification of an astronomical telescope is 10 and the focal length of eye-piece is 20 cm. The focal length of objective lens is

$\frac{1}{200} cm$
2 cm
200 cm
100 cm

152.

To get three images of a single object, one should have two plane mirrors at an angle of

60°
90°
120°
30°

153.

When a ray is incident on a medium of refractive index n at Brewster's angle,it gets

totally reflected
totally absorbed
circularly polarised
plane polarised

154.

A convex lens of focal length 12 cm is made up of a glass of refractive index $\frac{3}{2}$ .When it is immersed in a liquid of refractive index $\frac{5}{4}$ , its focal length will be

15 cm
6 cm
30 cm
24 cm

155.

A diver, at a depth of 12 metre from the surface of the water, sees the sky within a cone whose half vertex angle is : $(a^{μ_{w}} = \frac{4}{3})$

cos⁻¹ $(\frac{4}{3})$
sin⁻¹ $(\frac{4}{3})$
90 $°$
sin⁻¹ $(\frac{3}{4})$

156.

Consider telecommunication through optical fibres. Which of the following statements is not true?

Optical fibres can be of graded refractive index
Optical fibres are subjected to electromagnetic interference from outside
Optical fibres have extremely low transmission loss
Optical fibres may have homogeneous core with a suitable cladding

157.

An astronomical telescope has a large aperture to

reduce spherical aberration
have high resolution
increase span of observation
have low dispersion

158.

Focal length of a lens is +10 cm and its refractive index is 1.4, it is dipped in a liquid of refractive index 1.6, then its focal length becomes

- 16 cm
+ 32 cm
+ 16 cm
- 32 cm

159.

Two lenses have powers equal to +2 D and -4 D respectively, the power of combination will be

160.

The colour of a red cloth in green light appears

red
green
orange
black

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