Wave-Particle Duality of Light

wave theory of light

Things Needed

  • Table
  • Tape
  • Needle
  • Dark Room
  • Flat Wall
  • Printer Paper (White)
  • Laser (Use carefully)

How to do

  1. Try to fold and unfold the printer paper sheet simultaneously so that it could stay upright.
  2. Pierce a tiny hole in the printer paper with the needle provided.
  3. Make the printer paper stand upright on the table that would be a minimum ten feet far from the wall on which you would like to project the laser light onto.
  4. Use the tape for loading the laser pointer to a static base like big fat books. Afterwards, place the loaded laser on the table.
  5. Switch on the laser beam. The laser angle should be adjusted in such a way that the laser should pass through the paper hole and then to the wall.
  6. Pierce another hole on the paper adjacent to the existing one in such a way that both are close next to one another while ensuring not to create a larger hole.
  7. Shift the laser beam in such a way that the laser passes through both the holes. Try to observe the shapes that are created on the wall.
  8. Try covering one of these holes with a small piece of paper while sparing the other hole.

What happens next

After the experiment, you would have noticed that there is a block of light comes as output when the laser beam travels through one hole whereas there are stripes of light blocks when it travels through both the holes. When we cover one of the holes, the stripes would disappear all of a sudden. What happens actually is that photons are moving through both the holes and interfering with one another like waves in water almost similar to light patterns like ripples in a pool.

From this experiment, one could understand that only two things would happen during a wave interference viz. Waves that are in phase would combine to form a stronger wave whereas the waves that are out of phase would cancel each other out and weaken it eventually.


Practise This Question

 If A is in the III quadrant, 3 tan A –4 = 0 then 5 sin 2A + 3 sin A + 4 cos A=