  We determine the slope of the near infrared extinction power law
(A$_{\lambda} \propto \lambda^{-\alpha}$) for 8 regions of the Galaxy between
l$\sim27^{\circ}$ and $\sim100^{\circ}$. UKIDSS Galactic Plane Survey data are
compared, in colour-colour space, with Galactic population synthesis model data
reddened using a series of power laws and convolved through the UKIDSS filter
profiles. Monte Carlo simulations allow us to determine the best fit value of
$\alpha$ and evaluate the uncertainty. All values are consistent with each
other giving an average extinction power law of
$\alpha$=2.14$^{+0.04}_{-0.05}$. This is much steeper than most laws previously
derived in the literature from colour excess ratios, which are typically
between 1.6 and 1.8. We show that this discrepancy is due to an inappropriate
choice of filter wavelength in conversion from colour excess ratios to $\alpha$
and that effective rather than isophotal wavelengths are more appropriate. In
addition, curved reddening tracks, which depend on spectral type and filter
system, should be used instead of straight vectors.
