11)Permanent magnet can be made from
a) cobalt
b) Aluminium
c) zinc
d) lead
12) Compton effect is associated with
a) positive rays
b) b-rays
c) y-rays
d) X-rays
13) Which of the following particles is unstable
a) proton
b) electron
c) photon
d) neutron
14)Which of the following is not a semiconductor
a) germanium
b) silicon
c) arsenic
d) all of these
15) The resistance of a pn junction in forward bias is
a) zero
b) low
c) high
d) infinite
16)The space waves which are affected seriously by atmospheric conditions are
a) MF0
b) HF
c) VHF
d) UHF
17)Which one among the following has the highest energy?
a) blue light
b) green light
c) red light
d) yellow light
18) The power of lens is-2D.What is its focal length?
a) 2 m
b) 1.5 m
c) 1.0 m
d) 0.5 m
19) A radar beam consist of
a) X-rays
b) infrared rays
c) ultraviolet-rays
d) microwaves
20) When a body is immersed in a liquid,it force acting on it is—
a) Upthrust
b) Weight
c) Mass
d) Both