A ray of light only travels from air into glass without bending if it strikes the surface at a specific angle, known as the normal angle.

Here's why:

* Refraction: When light travels from one medium to another (like air to glass), its speed changes. This change in speed causes the light to bend, a phenomenon called refraction.

* Normal Angle: The normal angle is the angle at which a ray of light hits a surface perpendicularly (forming a 90-degree angle).

* No Bending: When light hits a surface at the normal angle, it doesn't change direction because the speed change is equal in all directions. There is no component of the light's velocity that is affected differently by the change in speed.

In summary:

* Normal angle: No bending

* Any other angle: Bending (refraction)

It's important to note that light will always bend *slightly* due to the change in speed, even at the normal angle. However, this bending is usually too small to be noticeable.