  We study the polarization efficiency (defined as the ratio of polarization to
extinction) of stars in the background of the small, nearly spherical and
isolated Bok globule CB4 to understand the grain alignment process. A decrease
in polarization efficiency with an increase in visual extinction is noticed.
This suggests that the observed polarization in lines of sight which intercept
a Bok globule tends to show dominance of dust grains in the outer layers of the
globule. This finding is consistent with the results obtained for other clouds
in the past. We determined the distance to the cloud CB4 using near-infrared
photometry (2MASS JHKS colors) of moderately obscured stars located at the
periphery of the cloud. From the extinction-distance plot, the distance to this
cloud is estimated to be ($459 \pm 85$) pc.
