The apparent depth of water in cylindrical water tank of diameter 2R cm is reducing at the rate of  x cm/minute when water is being drained out at a constant rate. The amount of water drained in  c.c. per minute is ( n₁ = refractive index of air, n₂ = refractive index of water)

• $\frac{\mathrm{x\pi } {\mathrm{R}}^2 {\mathrm{n}}_1}{{\mathrm{n}}_2}$

• $\frac{{\mathrm{x\pi R}}^2 {\mathrm{n}}_2}{{\mathrm{n}}_1}$

• $\frac{2\mathrm{\pi R} {\mathrm{n}}_1}{{\mathrm{n}}_2}$

• $\mathrm{\pi }$R²x

Assertion: Specific gravity of a fluid is a dimensionless quantity.

Reason: It is the ratio of density of fluid to the density of water.

• 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: Diamond glitters brilliantly. 

Reason: Diamond does not absorb sunlight.

• 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 resolving power of a telescope is more if the diameter of the objective lens is more.

Reason:  Objective lens of large diameter collects more
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

An object is immersed in fluid. In order that the object becomes invisible, it should

• behave as  perfect reflector

• absorb all light falling on it

• have refractive index one

• have refractive index exactly matching with that of the surrounding fluid

An endoscope is employed by a physician to view the internal parts of a body organ. It is based on the principle of

• refraction

• reflection

• total internal reflection

• dispersion

In an experiment to find the focal length of a concave mirror a graph is drawn between the magnitudes of u and v. The graph looks like 

An astronaut is looking down on earth's surface from a space shuttle at an altitude of 400 km.
Assuming that the astronaut's pupil diameter is 5 mm and the wavelength of visible light is 500 nm, the astronaut will be able to resolve linear objects of the size about

• 0.5 m

• 5 m

• 50 m

• 500 m

129.

Assertion: Owls can move freely during night. 

Reason: They have large number of rods on their retina.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements

Brilliance of diamond is due to

• shape

• reflection

• cutting

• total internal reflection