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.

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

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

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.

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.

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.

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

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

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

• Lloyd's mirror

• Fresnel biprism

• Young's double slit

• Prism

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

• $\sqrt{{\mathrm{d}}_1 {\mathrm{d}}_2}$

• d₁ d₂ 

• (d₁ + d₂ )/ 2

• $\sqrt{\raisebox{1ex}{${\mathrm{d}}_1$}\!\left/ \!\raisebox{-1ex}{${\mathrm{d}}_2$}\right.}$