Light
is
____________________
within
a
certain
portion
of
the
electromagnetic
spectrum
.
The
word
usually
refers
to
visible
____________________
,
which
is
the
____________________
that
is
visible
to
the
____________________
and
is
responsible
for
the
____________________
.
Visible
light
is
usually
defined
as
having
____________________
in
the
range
of
400
?
700
nanometers
(
nm
)
,
or
4
.
00
×
10
?
7
to
7
.
00
×
10
?
7
m
,
between
the
____________________
(
with
longer
wavelengths
)
and
the
____________________
(
with
shorter
wavelengths
)
.
This
wavelength
means
a
____________________
range
of
roughly
430
?
750
terahertz
(
THz
)
.
The
primary
properties
of
visible
light
are
intensity
,
propagation
direction
,
frequency
or
wavelength
spectrum
,
and
____________________
,
while
its
____________________
in
a
____________________
,
299
,
792
,
458
meters
per
second
,
is
one
of
the
fundamental
constants
of
nature
.
Light
is
also
used
in
various
other
fields
like
____________________
,
____________________
,
and
____________________
.
The
main
source
of
light
on
Earth
is
the
____________________
.
