**CBSE NOTES CLASS 12 PHYSICS **

**CHAPTER 10 WAVE OPTICS**

**Double slit vs single slit patterns**

In the double-slit experiment, we must note that the pattern on the screen is actually a superposition of single-slit diffraction from each slit or hole, and the double-slit interference pattern. It shows a broader diffraction peak in which there appear several fringes of smaller width due to double-slit interference.

The number of interference fringes occurring in the broad diffraction peak depends on the ratio $\frac{d}{a}$, that is the ratio of the path difference to the width of a slit. In the limit of ‘a’ becoming very small, the diffraction pattern will become very flat and we will observe the two-slit interference pattern.