Assertion:  A secondary rainbow have inverted colours than the primary rainbow. 

Reason:  The secondary rainbow is formed by single 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.

Resolving power of reflecting microscope increase with

• decrease in wavelength of incident light

• increase in wavelength of incident light

• increase in diameter of objective lens

• none of these

The near point of distinct vision is at 1 m for an elderly person. What power of lens is to be used to bring the near point to the minimum distance of distinct vision (25 cm)?

• 2.5 D

• 3 D

• 3.5 D

• 4 D

In a Young's double slit experiment the intensity of light when slit is at distance A from central is I. What will be the intensity at the distance of slit is $\frac{\mathrm{\lambda }}{6}$?

• $\frac{\mathrm{I}}{6}$

• $\frac{\mathrm{I}}{12}$

• $\frac{3}{4}\mathrm{I}$

• $\frac{\mathrm{I}}{6}$

Polaroid glass is used in sun glasses because

• it reduces the light intensity to half on account of polarisation

• it is fashionable

• it has good colour

• it is cheaper

In a Young's double slit experiment the spacing between the slits is 0.3 mm and the screen is kept at a distance of 1.5 m. The second bright fringe is found 6 mm from the central fringe. The wavelength of the light used in the experiment is

• 625 nm

• 600 nm

• 550 nm

• 500 nm

47.

Assertion: When light ray is incident at polarising angle on glass, refracted light is partially polarised. 

Reason:  The intensity of light decreases in polarisation.

• If both assertion and reason are true and reason 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: A laser beam of 0.2 W power can drill holes through a metal sheet, whereas a 1000 W torch-light cannot. 

Reason: The frequency of laser light is much higher than that of torch light.

• 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 Young's double slit experiment, fringe order is represented by m, then fringe width is

• Independent of m

• Directly proportional to m

• Directly proportional to ( 2m + 1 )

• Inversely proportional to (2m + 1 )

A light ray is incident on a glass slab, it is partially reflected and partially transmitted. Then the reflected ray is

• completely polarised and highly intense.

• partially polarised and poorly intense.

• partially polarised and highly intense.

• completely polarised and poorly intense.