Diffraction
Although light travels in a straight line, this rule that governs light may not
always so. For instance, take light rays passing through a narrow slit. This time, the
norm does not take place instead light diffracts.
Diffraction is the ability of light to
travel round corners and obstacles amist their pathways.
The length of slit will differ the angle of diffraction.
Thus, when the slit is very narrow diffraction may be evidently observed but when the slit
is wide enough, diffraction may or may not take place and can probably not be easily
determined.
Based on Thomas Young Huygen's principle, this bending
states that on a wave frotn all points serve to be sources of points. Thus, this justifies
why light reaches an obstacle with the exception of all other blocked wave fronts, the
light will behave as if it is the sole source of point and diffract instead of travelling
straight.
Interference
It takes place when two or more light waves go past a
point simultaneously, the instantaneous wave amplitudes will add up and result in
the formation of a new wave. There are mainly 2 types of interference as shown below
; -
Constructive Interference is when the
light waves reinforce one another to form a stronger wave.
Destructive interference takes place when
the instantaneous wave amplitudes are equilvalent and they cancel out each other.
You may then ask "How does interference work
then?"
As mentioned, diffraction takes place when light shines
through a narrow slit. What happens when it passes through a screen which possess 2 slits?
Due to close proximity, there will be two light sources and diffraction takes place again.
As the light rays passes through each of the ray, they will meet. The rays might meet by
side or out of step. Constructive intereference takes place when they meet in step.
Destructive interference occurs when the rays cancel out each other. When these 2 types
interference take place, bright and dark circles form on the screen. This observation thus
makes in sight intereference. In other words, intereference can be produced by anything
that causes light to separate into waves either in the case of reinforcing them or
cancelling them out.
