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CBSE

Subject

Physics

NEET Physics : Ray Optics and Optical Instruments

Multiple Choice Questions

91.

A far sighted person has his near point 50 cm, find the power of lens he should use to see at 25 cm, clearly.

+ 1 D
+ 2 D
- 2 D
- 1 D

92.

A convex lens of refractive index $\frac{3}{2}$ has a power of 2.5 D in a liquid of refractive index 2, then the new power of the lens is

$-$ 1.25 D
$-$ 1.5 D
1.25 D
1.5 D

93.

Two lens of focal lengths -20 cm and + 10 cm are put in combination, find the power of the combination

- 1 D
- 2 D
+ 5 D
+ 2 D

94.

Assertion: The focal length of objective lens in telescope is much more than that of eye piece.

Reason: Telescope has high resolving power due to large focal length.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

95.

Which out of the following, cannot produce two coherent sources?

Lloyd's mirror
Fresnel biprism
Young's double slit
Prism

96.

Assertion: Microscope magnifies the image.

Reason: Angular magnification for image is more than object in microscope.

If both assertion and reason are true and reason is correct explanation of assertion.
If both assertion and reason are true but reason is not correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

97.

For a person near point of vision is 100 cm. Then the power of lens he must wear so as to have normal vision, should be

+ 1D
$- 1$ D
+ 3D
$- 3$ D

98.

Assertion: Magnification of a convex mirror is always positive, but that of a concave mirror may be both positive or negative.

Reason: It depends on the sign convention chosen.

If both assertion and reason are true but reason is the correct explanation of assertion.
If both assertion are reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is not true.
If both assertion and reason are false.

99.

Assertion: When a white light is passed through a lens, violet light is more refracted than red light.

Reason: Focal length for red light is greater than violet.

If both assertion and reason are true and reason is the correct expalnation of assertion.
If both assertion and reason are true but reason not the correct explanation of assertion.
If assertion is true but reason is false
If both assertion and reason are false.

100.

In a concave mirror, an object is placed at a distance d₁ from the focus and the image is formed at a distance d₂ from the focus. Then the focal length of the mirror is

$\sqrt{d_{1} d_{2}}$
d₁ d₂
(d₁ + d₂ )/ 2
$\sqrt{\frac{d_{1}}{d_{2}}}$

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