1. Example
Example 3: This experiment demonstrates the interference of light. S1 S2 S
single slit slide
light source
translucent
screen
interference
fringe

2. Example
Two very narrow, parallel slits, S1 and S2, are illuminated by light from a single slit, S, which is parallel to S1 and S2 and placed in front of a strong monochromatic light source.

3. Example a) What is the purpose of the single slit?
The light source emits light waves in different and constantly varying phases. The single slit diffracts the light so that the phase of the wavefront is constant.

4. Example End b) What happens to the interference pattern when
(i) slit S is widened?
The fringes disappear.
(ii) the separation between S1 and S2 is increase?
The separation between the fringes decrease.
(iii) slit S1 is covered?
The fringes disappear.
End