A person uses + 1.5 D glasses to have normal vision from 25 cm onwards. He uses a + 20 D lens as a simple microscope to see an object. What is the maximum magnifying power if he uses the microscope without glasses.

• 8

• 9

• 10

• 11

252.

Assertion:  In optical fibre, the diameter of the core is kept small. 

Reason:  The smaller diameter of the core ensures that the fibres should have incident angle more than the critical angle required for total internal reflection.

• 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.

Assertion: The frequencies of incident, reflected and refracted beam of monochromatic light passing from one medium to another are the same. 

Reason: The incident, the reflected and refracted rays are coplanar.

• 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.

The length of deviation for a glass prism is equal to its refracting angle. The refractive index of glass is 1.5. Then the angle of prism is

• 2 cos^-1(3/4)

• sin^-1(3/4)

• 2 sin^-1(3/2)

• cos^-1(3/2)

Assertion:  The edges of the images of white object formed by a concave mirror on the screen appear white. 

Reason: Concave mirror does not suffer from chromatic aberration.

• 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.

The frequency of a light wave in a material is 2 × 10¹⁴ Hz and wavelength is 5000 A^o. The refractive index of material will be

• 1.50

• 3.00

• 1.33

• 1.40

Assertion:  If optical density of a substance is more than that of water then the mass density of substance can be less than water. 

Reason:  Optical density and mass density are not related.

• 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.

Assertion: The sun rises some time before the actual sun-rise.

Reason:  Because of the refraction through the different layers of atmosphere.

• 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.

Assertion: Resolving power of a telescope depends only on wavelength.

Reason:  This is proportional to square of wavelength.

• 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.

In a convex lens of focal length F, the minimum distance between an object and its real image must be

• 3F

• 4F

• $\frac{3}{2}$F

• 2F