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

Question : 16

The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is the reason ?

a) The density of water is maximum at 4°C.

b) Since the surface of the lake is at the same temperature as the air, no heat is lost.

c) Ice is a bad conductor of heat.

d) None

Question : 17 [UP UDA/LDA (Pre) 2002]

Two astronauts cannot hear each other on the Moon’s surface, because

a) No atmosphere on the Moon

b) They wear special space suits on the Moon

c) Their ears have stopped working on the Moon

d) The sound travels much more slowly on Moon

Question : 18

The velocity of sound in any gas depends upon

a) intensity of sound waves only

b) wavelength of sound only

c) density and elasticity of gas

d) amplitude and frequency of sound

Question : 19 [UPPCS (Pre) 2003]

Consider the following statements.

1. Fibre optics is based on the principle of total internal reflection.
2. In an optical fibre communication system, power consumption is extremely low.
3. Optical fibre communications are free from radio frequency interference.
4. In India, Reliance Group of Industries is engaged in the manufacture of the optical fibre.

a) 1, 3 and 4

b) 1, 2 and 4

c) 1, 2 and 3

d) 2, 3 and 4

Question : 20 [MPPCS (Pre) 2005]

Decibel is used to measure

a) Sugar in urine

b) Sound in atmosphere

c) Haemoglobin in blood

d) Particles in air