State what is meant by the principle of superposition.
Coherent light with wavelength $590\,\text{nm}$ is incident normally on a double slit, as shown in Fig. 6.1. The slit separation between A and B is $1.4\,\text{mm}$. The distance from the double slit to the screen is $2.6\,\text{m}$. At point P on the screen, the path difference for light reaching P from slits A and B is zero. Determine the separation of bright fringes on the screen near point P.
As shown in Fig. 6.1, coherent light with wavelength $590\ \text{nm}$ is incident normally on a double slit.
Fig. 6.2a and Fig. 6.2b respectively show how the displacement $x$ of the light wave reaching point $P$ on the screen from slit $A$ and from slit $B$ varies with time.
State the phase difference for the waves forming the dark fringe adjacent to point $P$ on the screen.
Determine the ratio of the intensity of light at a bright fringe to the intensity of light at a dark fringe.