# Young's Double Slit Experiment

Physics

## example

### Write intensity as a function of height from centre of screen in YDSE for two coherent light sources of equal intensity

Example: A point source is emitting light of wavelength is placed at a very small height above a flat reflecting surface MN as shown in the figure. The intensity of the reflected light is of the incident intensity. Interference fringes are observed on a screen placed parallel to the reflecting surface at a very large distance from it. Find the shape of the interference fringes, on the screen.

Solution:
represents the another point source forms due to reflection from the mirror.
and
Let path difference at point P  be
Using,

which represents equation of circle as
Thus the fringes will be of Circular shape centered at O.

## example

### Problem on maximum and minimum intensity ratio calculation during interference

Example:
A point source is emitting light of wavelength is placed at a very small height above a flat reflecting surface MN as shown in the figure. The intensity of the reflected light is of the incident intensity. Inference fringes are observed on a screen placed parallel to the reflecting surface at a very large distance from it. Find the ratio of maximum to minimum intensities at P.

Solution:
Before reflection, intensity of light is (say) and after reflection it becomes

So,

## example

### Problems on points on screen with minimum and maximum intensity in YDSE

Example: A screen is placed away from a single narrow slit. Find the slit width if the first minimum lies on either side of the central maximum. (wave length )

Solution:

## definition

### Describe the importance of YDSE

Historically, Young's Double slit experiment, when it was first carried  out by Young in 1801, demonstrated that light was a wave, which seemed  to settle for once and all the debate whether light was corpuscular  (particle-like) or wave. Up until that time, Newton's corpuscular was  the prevailing view of light, in spite of alternate explanations such as  Huygens' wave front model (which had some serious shortcomings). After Young's demonstration of the wave properties of light, followed by work  by others such as Fresnel studying the interference and diffraction  properties of it, and especially after Maxwell's brilliant equations of  electromagnetism, physicists in the 19th century rejected Newton's  corpuscular theory and believed that light was a wave.