Light

Light

1. How It Travels

   • Light travels in straight lines at a very high speed.
     • Light is represented by rays, which are straight lines with an arrow to show the direction the light travels in.

2. When Light Hits Objects

   • Light comes from sources like the Sun, flames, light bulbs and hot objects. These objects are luminous.
   • Light reflects off some objects so we see them. These objects are non-luminous.
   • Light is absorbed by objects which appear black.

3. Reflection

   • Light reflects off a plane mirror so that the angle of incidence equals the angle of reflection. Angles are measured from the normal.
     • The image in a flat mirror appears as far behind the mirror as the object is in front of it.
     • The image in a flat mirror is the same way up as the object.
     • The image in a flat mirror is the same size as the object.

4. How Light Travels Through Objects

   • Light is stopped by opaque substances which cast shadows.
   • Light goes through translucent substances but breaks up so you cannot see things clearly through them.
   • Light goes through transparent things so you can see things through them. When light goes through we say it is transmitted.
   • Light bends when it passes from one transparent substance to another. This is called refraction.

5. Spectrum

   • When light can be split into a spectrum by a prism. The colours are red, orange, yellow, green, blue, indigo and violet.
     • Red filters let through red light and absorb the rest of the spectrum. Other colour filters work in a similar way.
     • A red object reflects red light and absorbs other colours so it will look black in pure green light. A blue object will appear black in pure red light because it absorbs red light and reflects blue light.