Light generally travels in straight lines through a medium. This is known as the principle of rectilinear propagation.

However, there are a couple of scenarios where light can appear to bend or curve:

* Refraction: When light passes from one medium to another (e.g., from air to water), it changes speed. This change in speed causes the light to bend at the boundary between the two mediums. This bending is called refraction.

* Diffraction: When light passes through a narrow opening or around an obstacle, it spreads out. This spreading is called diffraction. It can make the light appear to bend or curve around corners.

So, while light normally travels in straight lines, it can appear to bend or curve under certain conditions due to refraction and diffraction.