Here's why:
* Refraction: When light travels from one medium to another (like air to glass), it changes speed. This change in speed causes the light ray to bend, a phenomenon called refraction.
* Angle of Incidence: The angle at which the light ray hits the surface is called the angle of incidence.
* Normal Line: An imaginary line perpendicular to the surface at the point of incidence is called the normal line.
* Normal Incidence: When the angle of incidence is 0 degrees (meaning the light ray hits the surface perpendicularly), the light ray travels along the normal line and does not bend.
In other words, if the light ray is shining directly onto the glass surface, it will not bend.
It's important to note that this is a theoretical scenario. In real-world situations, it's very difficult to achieve perfect normal incidence. Even slight deviations from perpendicular will cause some degree of refraction.
