Q. On a rainy day, small oil films on water show brilliant colours. This is due to

? Interference

Q. Materials for rain-proof coats and tents owe their water-proof properties to

? surface tension

Q. RADAR is used for

? detecting and locating the position of objects such as aeroplanes

Q. Sound of frequency below 20 Hz is called

? Infrasonic

Q. On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because

? cohesion of mercury is greater than its adhesion with glass

Q. Moment of inertia is

? Tensor

Q. Of the following natural phenomena, tell which one known in Sanskrit as ‘deer’s thirst’?

? Mirage

Q. One thousand microns is equal to

? 10^-3m

Q. Sound travels at the fastest speed in

? Steel

Q. Light travels at the fastest speed in

? vacuum