<s>
which	O
is	O
equivalent	O
to	O
joules	B-Language
,	O
the	O
SI	O
unit	O
for	O
energy	O
as	O
defined	O
in	O
the	O
physical	O
sciences	O
.	O
</s>
<s>
where	O
X(f )	O
is	O
the	O
Fourier	B-Algorithm
transform	I-Algorithm
of	O
x(t )	O
.	O
</s>
<s>
Dividing	O
by	O
Zo	O
,	O
the	O
characteristic	O
impedance	O
of	O
free	O
space	O
(	O
in	O
ohms	O
)	O
,	O
the	O
dimensions	O
become	O
joule-seconds	O
per	O
meter2	O
or	O
,	O
equivalently	O
,	O
joules	B-Language
per	O
meter2	O
per	O
hertz	O
,	O
which	O
is	O
dimensionally	O
correct	O
in	O
SI	O
units	O
for	O
spectral	O
energy	O
density	O
.	O
</s>
