21)Optical fibre mainly used in communication is based on
a) Less absorption coefficient
b) Less scattering
c) Total internet reflection
22) If there was were no gravity , which of the following will not be there for a fluid ?
c) Archimeds’s upward thrust
d) Surface tension
23) Post office box is a device for measuring resistant based on the principle of
b) Meter bridge
c) Ohm meter
24) The phenomenon of bursting of hydrogen balloon is based on
a) Charle’s law
b) Boyle’s law
c) Henry’s law
d) Bernoulli’s law
25) The image from by an object of a compound microscope is
a) Virtual and enlarged
b) Virtual and diminish
c) Real and diminish
d) Real and enlarged
26) A mirror products magnified erect image of and object. The nature of the mirror is
d) Neither convex nor convene
27) What enables us to write on the black board with chalk?
28) By which one of the following , and old written material which cannot be read easily, can be read ?
a) a- ray
29) Which one of the following has given the centripetal force for a car moving on a road ?
a) Force of breaks
b) The driver of the car
c) Force by the steering wheel
d) Friction due to tyres
30) Which one of the following is correct when a body moving in a circular path with constant speed ?
a) The body has constant acceleration
b) The body has constant retardation
c) The body has variable acceleration
d) The body has constant velocity and variable speed