short questions ......

[avid_reader]

how is leakage of charge minimised in a van de graff generator ???

can a galvanometer be used to detect a.c current ???

why are microwaves used in radar ???

physical quantity used to measure optical density ???

Is free neutron a stable particle ???

why do we prefer a.c. over d.c. ???

[itz_me]

Hey,
physical quantity used to measure optical density ?
refractive index

[pkciit]

a neutron is always unstable

[pkciit]

microwaves due to their directional property can be treated as directed beams and they do not spread or bend around the corners of obstacle
they can be used to estimate speeds and identify flying objects in space

[avid_reader]

Thanx guys...it really helped....
.......do try and answer the rest.........

[kauser]

leakage can be reduced by increasing the pressure

galvanometer is not used because the net movement of the coil for a complete cycle of ac is zero

free neutron is unstable . in 13 mins it gives out a proton

ac is preferred because there is less power loss in transmission over longer distances.
2) it can be stepped up or down using a transformer