After making a good understanding of electronic band structure, which is inherently connected to the optical behavior of a semiconductor (Equ. 4), it is interesting to discuss the optical behavior of p-BCN. The optical response is calculated with the photon energy range of 0 eV to 20 eV. The incident polarized light is considered in inplane (E‖x), and out-of-plane (E‖z) directions, which are sufficient directions to describe the optical behavior of this 2D system. We have performed spin non-polarized calculations to investigate the important optical parameters such as the real ( 1 ( )) and imaginary ( 2 ( )) parts of dielectric functions, absorption coefficient ( ( )), electron energy loss function (ELF) (L( )), refractive index ( ( )), and reflectivity ( ( )). To make a comparison, we plot these optical parameters side by side (Fig. ) for both directions. It is well known that the optical response is determined by the amplitude and number of peaks in the optical response curves. Higher amplitude with a larger number of peaks in the in-plane direction demonstrates that the optical response of this monolayer is significantly better in E‖x than in E‖z. This optical anisotropy is attributed to the structural anisotropy of this monolayer. Considering this, we limit our optical calculations for in-plane direction only. Furthermore, we apply biaxial strain and calculate the optical responses to compare with the calculated strain-free value.