Why does light cast shadows

Skip to content. Can a flame have a shadow? Which thing has no shadow? Can a light source have a shadow? Can Light be Black? Mind-Blowing Dark Light Experiments! Sometimes, it travels a short distance — like when we switch on the lamp. Other times, light travels thousands of years — like the light from stars we see in the Milky Way.

It is easy to see our shadows when we are outdoors in the sunshine on a clear, bright sunny day, but do shadows form when an object blocks light from other sources? The answer is yes, but they may be difficult to see if the light source is not very bright has a low light intensity.

Shadows are also more definite sharper where there is contrast between the shadow and the lit surface, for example, a shadow on a white wall will be more easily seen. The size of the light source can sharpen or blur the shadow. A small spotlight like a cellphone torch forms a more distinct shadow than an overhead room light, but the sharpness of the shadow changes when the torch moves away from the object.

A shape of an object always determines the shape of its shadow. However, the size and shape of the shadow can change. These changes are caused by the position of the light source. When we are outside on a sunny day, we can see how our shadows change throughout the day. When the Sun is low on the horizon, the shadows are long. When the Sun is high in the sky, the shadows are much shorter. We can create the same effects indoors by changing the position of a torch as it shines on an object.

Although the shadow effects are the same, the reasons for the moving light source are very different. Particles make a shadow. Light makes a shadow. But be careful what we conclude. Before we jump to conclusions, let's look at shadows cast by sound. Sound shadows: short vs long wavelengths In this experiment, a small source of sound the pipe, with diameter 8 mm produces sinusoidal sound waves with known frequencies and wavelengths, in a room treated to reduce reflections and reverberation. Close above the the source, I hold a book above it.

Above that, I hold a microphone which I scan sideways. The sound track for one scan is shown in each experiment. So if you can a source of light and an object that is obstructing the path of the light,then a shadow is created. The length and shape of the shadow depends on the angle from which light was sourced. The source of light could be an infrared light. IR light is invisible to human eye. Yes, it casts a shadow which is only visible using a device which detects infrared light, like your phones camera.

Your eyes cannot see invisible light, but, invisible light e. Now then, how could we use an invisible light source let's stick with IR and create a shadow that is visible to the human eye. Here are a couple of possibilities:. You might also have to coat the back of the obstruction with a reflective coating of some kind to increase the reflected light level that would fall in the shadow region to make it look more realistic--otherwise, the shadow might appear too dark for the setup.

This possibility is of course not a real shadow--it's more of a pseudo shadow, if you will. This of course would create a visible light source from invisible radiant energy--which may not meet your criteria, however it would be sourced initially from an invisible light source.

This is similar to 1, but using higher energy invisible wavelengths. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?