Ray Optics Test...

Assertion The fluorescent tube is considered better than an electric bulb.
Reason Efficiency of fluorescent tube is more than the efficiency of electric bulb.

Assertion The polar caps of earth are cold in comparison to equatorial plane.
Reason The radiation absorbed by polar caps is less than the radiation absorbed by equatorial plane.

Assertion A concave mirror and convex lens both have the same focal length in air. When they are submerged in water, they will have same focal length.
Reason The refractive index of water is smaller than the refractive index of air.

Assertion In optical fibre, the diameter of the core is kept small.
Reason This smaller diameter of the core ensures that the fibre should have incident angle more than the critical angle required for total internal reflection.

Assertion The mirrors used in search lights are parabolic and not concave spherical.
Reason In a concave spherical mirror the image formed is always virtual.

Assertion The cloud in sky generally appear to be whitish.
Reason Diffraction due to cloud is efficient in equal measure at all wavelengths.

Assertion Just before setting, the sun may appear to be elliptical. This happens due to refraction.
Reason Refraction of light ray through the atmosphere may cause different magnification in mutually perpendicular directions.

Assertion Critical angle of light passing from glass to air is minimum for violet colour.
Reason The wavelength of violet light is greater than the light of other colours.

Assertion We cannot produce a real image by plane or convex mirrors under any circumstances.
Reason The focal length of a convex mirror is always taken as positive.

Assertion Diamond glitters brilliantly.
Reason Diamond does not absorb sunlight.