Light from a helium-neon laser passes through a narrow slit and is incident on a screen 2.4m distance from the slit. The graph below shows the variation with intensity I of the light on the screen of distance x along the screen.

In the figure, two radio-frequency point sources S1 and S2, separated by distance d = 1.6 m, are radiating in phase with A = 0.4 m. A detector moves in a large circular path around the two sources in a plane containing them. How many maxima does it detect? Number x S₁ S2 Units

A perfectly flat piece of glass (n = 1.50) is placed over a perfectly flat piece of black plastic (n = 1.20) as shown in the figure a. They touch at A. Light of wavelength 600 nm is incident normally from above. The location of the dark fringes in the reflected light is shown on the sketch of figure b. (a) How thick is the space between the glass and the plastic at B? (b) Water (n = 1.33) seeps into the region between the glass and the plastic. How many dark fringes are seen when all the air has been displaced by water? (The straightness and equal spacing of the fringes is an accurate test of the flatness of the glass.) (a) (b) A Glass =1.50 Plastic n=1.20 B

A red laser of wavelength 632.8x10-9 m is directed horizontally towards a diffraction grating. The separation between slits on the grating is 2.54x10-5 m. What angle is a 2nd order bright spot is seen at? Use the following equation to calculate the angle. mλ = d sin 0