03. Light (basics)

LEARNING TARGETS

State that light is a for of energy and travels in waves

State which objects are luminous and non-luminous

Outline how the size of light source produces umbra and penumbra

Define terms such as transparent, translucent, opaque

ATL FOCUS

Organize and depict information logically - making notes during class

Light is an example of a Transverse wave. It is not a mechanical wave which means the vibrations within the wave are not due to the physical movement of matter (particles), but are actually a vibrating magnetic and electric field! Because light does not require particles to move it can even pass through the empty space of a vacuum. In fact light moving through empty space is the fastest thing in the universe, travelling 300 million metres every second!

Light generally travels in a straight line. If light can be transmitted through a medium (or material) then we call it transparent. If light cannot be transmitted through it then we call it opaque. Some objects allow some light to pass through them but an image cannot be formed (e.g. stained glass or tracing paper) and are called translucent.

The fact that light travels in a straight line means that opaque objects can cast a shadow. Shadows can be a total absence of light (umbra) or partial absence of light (penumbra).

Pinhole cameras have a very small hole at the front of them that allows light to come in from an object and form an image on the camera screen. The image is always inverted and the more holes you make the more images you get.

If you make the hole bigger the image gets brighter but it also losses clarity as essentially multiple images are forming on top of each other.