Light is indeed a transverse wave, despite the fact that it travels in a straight line. The transverse nature of light refers to the direction of the oscillations of its electric and magnetic fields, which are perpendicular to the direction of propagation.
In a transverse wave, the oscillations occur perpendicular to the direction of energy transfer. In the case of light, the electric and magnetic fields oscillate in mutually perpendicular planes as the wave propagates through space. This perpendicular oscillation is what makes light a transverse wave.
The straight-line propagation of light occurs because of the wave nature of light and the absence of significant obstacles or disturbances to its path. When light encounters a medium with a different refractive index, such as a lens or a prism, it may undergo refraction and change its direction, but it still continues to propagate as a transverse wave.
It's important to note that while light travels in a straight line in a uniform medium, it can exhibit different behaviors when interacting with obstacles, diffraction gratings, or other optical elements. These phenomena arise due to the wave nature of light and its ability to interact with different structures and materials.