There is no change of angle (bending) of the light rays. Each wavelength is slowed the same amount in the glass and is increased the same amount as it leaves the glass.

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/mch/refr/more.rxml
http://csep10.phys.utk.edu/astr162/lect/light/dispersion.html
http://en.wikipedia.org/wiki/Light_source

I hope this helps. Thanks for asking.

When a beam of white light passes perpendicularly through a flat pane of glass, it is not dispersed into a spectrum? Why not?

Well, that's a good question! It seems like glass just isn't a fan of rainbows. Maybe it's got a personal grudge against ROYGBIV or something. But seriously, when light passes perpendicularly through a flat pane of glass, the different wavelengths of light don't get spread out like they do when they pass through a prism or a droplet of water. Instead, they just slow down a bit while they're in the glass and then speed back up to their original velocity when they exit. It's like they're in a rush to get through the glass without causing any colorful commotion. So, the light rays remain parallel and undisturbed, keeping the white light intact. It's basically glass's way of saying, "No fancy light shows allowed!"

When white light passes through a flat pane of glass perpendicularly, it does not disperse into a spectrum because there is no change in the angle or bending of light rays. Each wavelength of light is slowed down by the same amount as it enters the glass, and it is then sped up by the same amount when it leaves the glass.

According to the laws of refraction, when light passes from one medium to another, such as from air to glass, its speed and direction change depending on the refractive index of the materials involved. In the case of a flat pane of glass, the angle of incidence and the angle of refraction are the same, which means the light rays pass through the glass without bending. Therefore, the white light remains undispersed and does not split into its constituent colors.

In order to observe the dispersion of white light into a spectrum, the light rays need to be incident at an angle other than perpendicular to the glass. This causes different wavelengths of light to refract at different angles, resulting in the separation of colors.

When a beam of white light passes through a flat pane of glass perpendicularly, it does not disperse into a spectrum because of a phenomenon called "dispersion." Dispersion is the splitting of white light into its constituent colors due to the variation in the refractive index of different wavelengths.

In this case, the absence of dispersion can be explained by the fact that the light rays passing through the glass pane do not undergo any change in angle (bending) as they enter or exit the glass. This means that each wavelength of light is slowed down by the same amount while passing through the glass and is then accelerated by the same amount as it leaves the glass.

The refractive index of a material determines how much light is slowed down while passing through that material. In the case of glass, the refractive index for different wavelengths of visible light is relatively constant, meaning that there is no significant variation in the amount of slowing down for different colors of light.

Since the different colors of light are not slowed down differently and remain in phase with each other, they do not separate into a spectrum upon passing through the glass pane. Therefore, the incident white light retains its original composition and does not disperse into different colors.

To understand this concept, you can refer to the resources you provided. The first link explains how light is refracted and introduces the concept of dispersion. The second link specifically discusses dispersion and the process of light splitting into a spectrum. The third link provides a general introduction to light sources and their properties, including dispersion.

By familiarizing yourself with the principles explained in these resources, you will gain a comprehensive understanding of why white light passing perpendicularly through a flat pane of glass does not experience dispersion and retain its original composition.