  Investigating the extinction properties in dense molecular clouds is of
significant importance for understanding the behavior of interstellar dust and
its impact on observations. In this study, we comprehensively examined the
extinction law in the Ophiuchus cloud across a wavelength range from
0.8$\,\mu\rm m$ to 8$\,\mu\rm m$. To achieve this, we analyzed NIR and MIR data
obtained from the UKIDSS GCS and the Spitzer c2d survey, respectively. By
fitting a series of color-color diagrams, we determined color-excess ratios
$E_{J-\lambda}/E_{J-K}$ for seven passbands. These ratios were then directly
converted to derive the relative extinction law $A_\lambda/A_K$. Our findings
demonstrate that the Ophiuchus cloud exhibits a characteristic of flat MIR
extinction, consistent with previous studies. Additionally, our results reveal
variations in the extinction law with extinction depth, indicating a flatter
trend from the NIR to MIR bands as extinction increases. Notably, our analysis
reveals no significant difference in the MIR extinction law among the four dark
clouds: L1712, L1689, L1709, and L1688. However, distinct variations were
observed in the extinction law for regions outside the dark clouds,
specifically L1688N and L1688W. These regions displayed lower color-excess
ratios $E_{J-\lambda}/E_{J-K}$ in the Spitzer/IRAC bands. This observation
lends support to the dust growth occurring in the dense regions of the
Ophiuchus cloud.
