When an object is transparent, light is able to travel through it so that anything placed behind the transparent object is still clearly visible. Clear glass is an example of a nearly transparent material. It is important to note that glass is considered a nearly transparent material, as it does reflect a minimal amount of light. A material that is completely transparent would actually be invisible. Whereas with an opaque object light is unable to travel through it and, therefore, nothing can be seen behind it. Concrete, wood and metal are examples of opaque materials.
With an abstract topic, such as how light travels through objects, children may become lost if it is only discussed with them. However, hands-on learning lends itself well to demonstrating the differences between transparency and opacity. Regardless of the children’s age, if you offer them various items and ask them if they can see through them, the distinction between the two terms will quickly become clear. Allowing the children to test various materials will make the learning engaging, increasing their retention rate of the key ideas.
By gathering some transparent and opaque materials, a school classroom can be transformed into a light laboratory. Have students look through a piece of clear plastic wrap; they will be able to see through to the other side since the wrap is transparent. On the other hand, when students attempt to look through a piece of cardboard, no light will pass through since cardboard is opaque. Students of any age can brainstorm hypotheses about which classroom objects they believe are transparent or opaque and can then test their own predictions.
An extension activity is to test the creation of shadows on transparent and opaque objects. Since light travels in a straight line, transparent objects allow light to pass directly through to the other side, eliminating the creation of a shadow. However, opaque objects block light from passing through and divert it, casting a shadow on the other side. Children can test this theory by using flashlights and shining them on various objects in a darkened room. For example, light will still pass through a piece of plastic wrap but will not pass through a piece of cardboard. The opaque piece of cardboard casts a shadow since it is blocking the light from passing through. Additionally, children can explore the effects on the size of the shadow as the flashlight is moved closer to (shadow will get bigger) and further away from (shadow will get smaller) the piece of cardboard.