Question

An arrangement is setup for obtaining interference fringes in a Young's double-slit experiment. Describe what will be seen on the screen if the arrangement is altered in each of the following ways:

a) The slit separation A is halved (Note that this is the distance between the individual slits and not the width of the actual apertures)

b) The distance D from slits to screen is doubled

c) The monochromatic light source is replaced with a white-light source

Answer 1

d) A piece of Polaroid is placed in front of each slit, the polarising directions of the polaroids being vertical for one slit and horizontal for the next.

Answer 2

*describe and explain.

Answer 3

I'm guessing the distance between maximum intensities will be more than doubled in a) but I do not know why. Thanks for any help!

Answer 4

The position of the center of the bright fringes is give by: \(y_m=\dfrac{m\lambda L}{d}\)

m is the order, \(\lambda \) is the wavelength of light, L is the distance from the two slits to the screen and d is the distance between the slits.

If you remove all constants from the equation you see that they have an inverse relationship: \(y_m=\dfrac{m}{d}\), so increasing d makes the spacing and the fringe width smaller.

You can use the initial equation (above) to make assertions when changing the variables. When in doubt just plug some numbers in.