16) Which one of the following planets is said to be ‘’twin sister’’ of the Earth?
17) A perfect black body has the unique characteristic feature as
a) a good absorber only
b) a good radiator only
c) a good absorber and a good radiator
d) Neither an absorber nor radiator
18) Cavitation is a special application property exhibited only by
a) audible sound
d) electromagnetic waves
19) Why laser is used in the pipe alignment?
a) They are directional in nature
b) They are coherent
c) They are monochromatic
d) None of the above
20) Which one of the following common devices works on the basis of the principle of mutual induction?