TEXT: REFRACTION OF LIGHT

Light travels in a straight line until it passes through another medium. When the light enters a different medium, like from air to water, the light refracts, changes speed and direction. This makes a pencil in a glass of water appear to be at a different bent angle in water than in the air.

Light slows down because the density (how close together molecules are) of the new medium, water, is greater than the density of the previous medium, air. Light travels slower through water than through air. So, the light that reaches your eyes is received at a slightly slower speed when it travels through water.

In a lab, or in space, when light travels through a vacuum, where there is no air or any other substance, it travels the fastest of all.

When light travels through a new medium, light refracts, and objects seen appear to bend.

TEXT: BENDING LIGHT

As you read the text, think about other objects in water. Does their appearance change in some way?

TEXT: PRISMS

Click the link to learn how prisms bend light, causing white light to split into a spectrum of colors.

VIDEO: MICROSCOPES

Click the link to watch the 3-minute video about microscopes and refraction.

Watch a Stanford Bioengineer explain how microscopes work, and how he was able to use micro-optics to build one out of paper with this video from KQUED's Science 2015 series. This video is part of our Engineering Is: Diagnosing Diseases with Origami Microscopes e-book. The e-book explores the science and engineering principles behind Manu Prakash’s Foldscopes project, and includes videos, interactives and media making opportunities.