e= Angle of emergence
A = refracting angle
r + r’ = Angle of a refraction
δ = deviation
i + e = A + δ                ---(i)
A = r1+ r2 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ---(ii)
Above relation connecting i. c., A + δ are shown above.
Under minimum deviation i = e, rt = r2 = r
From Eq. (i), we have
2 i = A + δ min
 Â
Hence proved.Â
(i) What is meant by:
(A) Spherical aberration?
(B) Chromatic aberration?
(ii) How can spherical aberration be reduced/minimized? Suggest any one method.
(i) Define Resolving Power of a simple astronomical telescope.
(ii) State one advantage of a reflecting telescope over refracting telescope.
ndeviated through a uniform electric field  for intensity 5 x 104 Vm-1 and a uniform magnetic fieldÂ
.
(i) Find the magnitude of magnetic flux density B of the magnetic field.
(ii) What is the direction of  is towards right andÂ
 is vertically downwards in the plane of this paper?