(a) Order of magnitude is defined as the power of 10 used to express the magnitude of a physical quantity under consideration, e.g.,
(i) Order of magnitude of time intervals of 1.2 x ${{10}^{-6}}$s
is-6.
(ii) Order or magnitude of distance of 4.5 x ${{10}^{6}}$
is + 6.
(b) 1 light year = 9.46 x ${{10}^{15}}$ m = ${{10}^{16}}$ m
Order of magnitude of light year is 16