Answers to Optics Worksheet



  1. The missing colours are red, green and blue.  When the disc spins it appears white. This tells us that white light is a mixture of all the colours.
  2. The three light sources that make the colours are red, green and blue.  They are called the primary colours of light because they can combine to make any other colour.
    If all the colours of light are blocked you get a black shadow.  Blocking only red light gives a cyan shadow, and just green gives a magenta shadow.

  3. If you have normal colour vision, you should see the number 10 in the left circle,57 in the middle and there should not be any number in the right circle.
  4. The light travels in straight lines and bounces off the sides of the tube. This effect (total internal reflection) is used to see inside the body.
  5. The mirror is concave.  The light rays are reflected inwards so they converge at a point.
  6. A light spectrum looks like a rainbow.   The two types of light you can not see are Ultra Violet and Infra Red. Infra Red can be detected by the heat.
  7. The light rays travel in a straight line and reflect off the sides of the tube in a zig-zag.
  8. When student 1 is lit she sees her own reflection.  The light ray should be drawn from her face to the mirror,then bouncing back off the mirror to her own eyes.  When student 2 is lit , student 1 sees student 2.   The light rays should be drawn passing from student 2's face, through the mirror to student 1's eyes.
  9. The shadow in the shadow box stays after you move away because the screen absorbs the light energy and carries on glowing for a while.   Where the light was blocked from the screen there is a shadow.
  10. Mirror 1 is a convex mirror that gives a short wide image.  Mirror 2 is a concave mirror that gives a tall, narrow image.   Mirror 3 is a flat mirror that gives a normal image.
  11. The concave mirror reflects the light inwards so it appears to come from a higher point.   This is the opposite to the convex mirror shown in the diagram.