Interference of Light Waves:

Young's Double$-$Slit Experiment

Textbook p

Vocabulary

incoherent

interference fringe

minima

monochromatic

maxima

MAIN IDEA: Young's experiment produced a series of light and dark fringes on a screen placed in the path of the light, with a pattern that resembled the results of interference of water waves in a ripple tank.

Early experiments to demonstrate diffraction of light did not succeed. Why not?

$($a$)$ The nodal lines were too far apart to observe.

$($b$)$ The wavelength of light was too large.

$($c$)$ The sources were not in phase.

$($d$)$ all of the above

An example of a monochromatic light source is a$($n$)$

$($a$)$ incandescent light bulb

$($b$)$ fluorescent light

$($c$)$ neon light

$($d$)$ laser

Is the following statement true or false? If you think the statement is false, rewrite it to make it true: A monochromatic light source must be coherent.

MAIN IDEA: The locations of bright fringes are given by dsin$=m,m=0,1,2,3,$dots. The locations of dark fringes are given by dsin$=(n-\frac{1}{2}),n=0,1,2,3,$dotsdots. For a viewing screen at a distance $L,$ the $m$ th$-$order bright fringe is at location $x_m=\frac{mL}{d}.$ The $n$ th$-$order dark fringe is at location $x_n=(n-\frac{1}{2})\frac{L}{d}.$ Young's diffraction experiment provided evidence for the wave nature of light.

$4.$ After Young succeeded in demonstrating diffraction and interference in light, the wave theory could explain all properties of light except one. Which was it$?$

$($a$)$ refraction

$($b$)$ rectilinear propagation

$($c$)$ propagation through a vacuum

$($d$)$ dispersion

$5.$ Is the following statement true or false? If you think the statement is false, rewrite it to make it true: If the slits producing an interference pattern can be moved closer together, the bright fringes will move farther apart.