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Name:  Suresh M.
Status: student
Age: 30s
Location: N/A
Country: N/A
Date: 2000-2001


Question:
Dear Sir/Madam,

This question is related to the dual nature of light. The condition is :- Suppose two persons are standing at a same elevation(height) and are of same height and they are looking at two different objects kept at cross at same height and elevation, now the two objects are visible to the persons because of reflection of light from the objects.

The question is :- 1) Now considering light as wave first; the light at the point of cross in the 1st case of constructive interference should make both the persons both the objects visible at the same time and in the 2nd case of destructive interference the light should get destruct and both the persons should not see the object they are looking at; 2) Now considering the light as a particle at the point of cross the light(in the form of particles) should collide and change their direction, as a result the persons should see the object at the cross rather than at what he is looking so both of them should see the cross objects but its not like that WHY ?


Replies:
Suresh,

First, you must realize that light is not a wave AND a particle. It is in fact neither one. It is light. Light has some properties that are the same as traditional waves. It has some properties that are the same as traditional particles. One of the more accepted models is wave packets: little bits of waves collected within small particle-like bundles. We don't really know what to call light. It has a frequency, it has a wavelength, it oscillates. In a traditional wave, more energy should result in a larger amplitude. Unlike standard waves, more light energy does not mean a stronger wave. More energy means more individual wave packets. Unlike standard waves, light waves carry momentum as well as energy. Also, light does not need a medium to carry it. Sound waves need air to carry it. Water waves need the surface of water. Like particles, light can pass through a vacuum.

When light reflects from a surface, wave interference rules apply. No scientis knows why this must be so. It is how reality works. Scientists just try to understand it. Actually, reality is a great distance from being complete understood.

Dr. Ken Mellendorf
Illinois Central College



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