12.7 Phenomena Related to Refraction

12.7 Phenomena Related to Refraction

Apparent Depth

Figure 1.0

Apparent Depth is the depth that an object appears to be at due to the refraction of light at the transparent medium. Our eyes interpret the refracted light as coming from a source along the line of sight. An example would be cleaning a fish tank. When you put the net in to the water to remove the fish, more times than not, you will miss the fish, because, the object is travelling from a less dense medium to a denser medium, it will result in refraction, causing a virtual image, and the net to be bent. (The light is bending towards the normal.) Therefore the fish is appeared to be deeper than it actually is. (see Figure 1.0)

Mirages

A mirage is a virtual image that forms as a result of refraction and total internal reflection within the Earth's atmosphere. Light waves from the sun travel straight through the atmosphere to our eyes. However, light travels at different speeds through hot and cold air. Mirages occur when the ground is hot, and the air is cool. For example; in the desert, the hot sand warms a layer of air just above the ground. When light moves from the cool air medium in to the hot air medium- it is refracted- and therefore bent. The "puddle" that we see appear on the ground is the reflection of the light bending (refraction) from the sky. Therefore the light from the sky appears to be on the ground in front of us, which creates the image of a puddle. See the video provided below, for an in depth explanation.

 Dispersion of Light and Rainbows

Dispersion is the separation of white light into its constituent colours (the spectrum.) Each colour of visible light (ROYGBIV) travels at different speed when it travels through glass prisims. That is why light refracts more than the other colours of the spectrum. Red light is refracted the least of all the colours in the spectrum. This is how rainbows are created in glass prisms. (See Figure 1.1) The video provided below will explain this concept in greater detail.

Figure 1.1

When white light enters a raindrop, dispersion occurs. The seven colours of the rainbow are produced. When this light hits the back of the raindrop, partial reflection occurs. The light continues to refract once it moves from the raindrop into the atmosphere. People only see 1 colour from each drop because the majority of the other colours miss our eyes. Therefore a rainbow is a mix of drops at different elevations. The shape of the rainbow comes from the different angles of refraction that the colours are producing. (See Figure 1.3) Double rainbows occur from two internal reflections, that are always higher in the sky compared to the original rainbow and the order of the colours are reversed. (See Figure 1.4)

Figure 1.4

Figure 1.3

For additional information go to:

Rainbows & Refraction

Phenomenas Related to Refraction

Bending Sunlight

By:  J.C. and M.T.