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CBSE

NEET Physics : Ray Optics and Optical Instruments

Multiple Choice Questions

201.

A convex lens of focal length 30 cm produces 5 times magnified real image of an object. What is the object distance?

36 cm
25 cm
30 cm
150 cm

202.

Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is

203.

If the focal length of the eye-piece of a telescope is doubled, its magnifying power (m) will be

2 m
3 m
$\frac{m}{2}$
4 m

Short Answer Type

204.

A ray of light travelling inside a rectangular glass block of refractive index $\sqrt{2}$ is incident on the glass-air surface at an angle of incidence of 45°. Show that the ray will emerge into the air at an angle of refraction equal to 90°.

Multiple Choice Questions

205.

A 2.0 cm object is placed 15 cm in front of a concave mirror of focal length 10 cm. What is the size and nature of the image ?

4 cm, real
4 cm, virtual
1.0 cm, real
None of these

206.

A plano-convex lens (f = 20 cm) is silvered at plane surface. Now focal length will be

20 cm
40 cm
30 cm
10 cm

207.

If x₁ be the size of the magnified image and x₂ the size of the diminished image in Lens Displacement Method, then the size of the object is

$\sqrt{x_{1} x_{2}}$
x₁x₂
x₁²x₂
x₁x₂²

208.

A beam of monochromatic blue light of wavelength 4200 $\overset{\circ}{A}$ in air travels in water of refractive index 4/3. Its wavelength in water will be.