Light, Heat, Thermodynamics, Wave Motion, Sound, Optics & Oscillations - Category Wise Question And Answer Practice Test With Solutions

Question : 21

Flash light equipped with a new set of batteries, produces bright white light. As the batteries wear out

a) it stops working suddenly while giving white light

b) the light intensity gets reduced with no change in its colour

c) light colour changes first to yellow and then red with no change in intensity

d) colour changes to red and also intensity gets reduced

Question : 22 [PSC (Pre) 2018]

Sound waves travel fastest in

a) Liquids

b) Gases

c) Solids

d) Vacuum

Question : 23 [PSC (Pre) 2018]

Given below are two statements, one labelled as Assertion (A) and other labelled as Reason (R).
Assertion (A):
A diamond sparkles more than a glass imitation cut to the same shape.
Reason (R):
The refractive index of diamond is less than that of glass.
In the context of the above two statements, which one of the following is correct?

a) (A) is true, but (R) is false

b) Both (A) and (R) are true, but (R) is not the correct explanation of (A)

c) Both (A) and (R) are true and (R) is the correct explanation of (A)

d) (A) is false, but (R) is true

Question : 24 [RAS/RTS (Pre) 2012]

The optimum sound level for human beings is

a) 60 dB

b) 120 dB

c) 90 dB

d) 100 dB

Question : 25

A hollow sphere is filled with water. It is hung by a long thread. As the water flows out of a hole at the bottom, the period of oscillation will

a) go on increasing

b) first increase and then decrease

c) first decrease and then increase

d) go on decreasing