Shadows
An object that absorbs or reflects light can hide another object from our view if it's placed in a way that any straight line from our eyes to the target object is broken by the hiding object. An object placed between our eyes and a light source can also prevent us from seeing the light source. This means there is an area behind any object where light from the source cannot reach. There is then a part of the screen that, lying in the object’s shadow, is dark because light is not reaching it, and we call this part a shadow.
The shape and size of the shadow produced on a screen, and the shadow area itself, are shown by shape, size, and the positioning of the object making the shadow. The area covered by the shadow grows as one carries on further behind the object. The size of the shadow formed on a screen is proportional to the distance between the screen and the light source. In other words, moving the screen so that its distance from the light doubles, without moving the object, will cause the shadow on the screen to double in size.
By rotating the object, the edge presented to the light source will change, changing the shape of the shadow on a screen. Also, since the shadow depends only on the edge presented to the light source, objects of different shapes can produce identical shadow shapes. Understanding the way shadows are created and attempting to notice shapes by their shadows are all good ways to strengthen students’ understanding of the way light grows. Shadows will not grow with distance behind the object in the same way.