You will need:
- CD
- Different light sources (normal bulb, LED bulb, tube light, etc.)
Discover something new while
understanding the basic properties of a CD.
INSTRUCTIONS
- Take your CD and keep it upside
down so that the reflective silver side may be facing up. - Now, try reflecting different light sources onto the reflective surface of the CD.
- Do you find any difference in the reflections from a normal bulb to a
LED bulb
RESULT
Firstly, a CD is comprised of an aluminium layer which is sandwiched between two layers of plastic. The aluminium has small pits on its surface in concentric circles. These pits store the information on the CD. When light is reflected onto the aluminium side, the light is reflected off the aluminium but not off the pits in between which work as a bad reflective surface. Secondly, the aluminium layer reflects light much like a mirror. Since light is made up of different colours, it is easy to see these colours once they have been broken down and reflected on the aluminium surface. A normal bulb is comprised of all the colours of the rainbow, hence you might see a smooth rainbow of colours reflecting back at you. An LED bulb, on the other hand, is comprised of only a few colours with a lot of empty space between the colours. This is thus reflected in the form of a few colours which are interspaced.
