In a series of recent investigations R. S. Krishnan (1934-8) demonstrated the existence of a new effect which will be called the Krishnan effect. It relates to the state of polarization of the light scattered by certain liquid or solid media in directions normal to the incident beam. To describe the effect let us denote with π the plane parallel to the direction of observation and to that of the incident beam. Since in the experiment this plane is usually horizontal we denote by
H
the intensity of those scattered light components which vibrate parallel to this plane, and by
V
those vibrating normal to π. In a similar manner subscripts
h
or
v
indicate whether the incident light vibrates parallel or normal to the plane. We distinguish therefore (see fig. 1) the four light components
H
h
,
H
v
,
V
h
and
V
v
. Following Krishnan the depolarizations are defined by
P
h
=
V
h
/
H
h
,
p
v
=
H
v
/
V
v
,
p
u
= (
H
h
+
H
v
)/(
V
h
/
V
v
).
p
u
is the depolarization for natural incident light. For most liquids the observations give, in agreement with the theories of temperature scattering,
H
h
=
V
h
=
H
v
, hence
p
h
= 1,
p
u
= 2
p
v
/(1+
p
v
). The Krishnan effect is the observation that in a number of liquid and solid systems
p
h
=
V
h
/
H
h
≠ 1, and
V
h
=
H
v
. Krishnan has called (2) the reciprocity relation. All observations have given
p
h
< 1, but none of the present theories exclude the possibility that
p
h
may assume values larger than 1.
On the theory of scattering of light
