1) In Young’s double-slit experiment slit #2 (bottom slit) is covered with a thin piece of glass. This slows down the light going to slit #2 and changes the relative phases of the light going to the slits. a) Assume that the glass is thick enough to retard the phase of the light going to slit #2 by p (180 degrees). What happens to the interference pattern? b) Assume that the glass is thick enough to retard the phase of the light going to slit #2 by p/2 (90 degrees). What happens to the interference pattern?

2) Briefly explain how Huygen sources make up a plane wave. (Diagrams!)

3) Why is there no interference pattern from the headlights of a distant car.

4) If one slit is covered in a two slit interference experiment, by what factor does the intensity at the center of the screen change?

5) What wavelength of visible light (450 nm < l < 700 nm) is reflected off a thin film that is 250 nm thick?

6) Red light (l=630 nm) illuminates the two glass plates shown below from the top. On the right side the plates are separated by 5 mm. How many bright red fringes are seen from above the plates?

7) HRW 35.34.

In the double-slit experiment of Fig. 35-10, the viewing screen is at distance D = 4.00m, point P lies at a distance y = 20.5cm fro the centre of the pattern, the slit separation d is 4.50μm, and the wavelength λ is 580 nm.

a) Determine where point P is in the interference pattern by giving the maximum or minimum on which it lies, or between which it lies.

b) What is the ratio of the intensity I_P at point P to the intensity I_cen at the centre of the pattern?

c) Plot the intensity of the light seen on the screen as a function of y from y = 0 to y = 30 cm.

8) What would happen to if a complete Young’s double-slit experiment were immersed in water having an index of refraction of n = 1.3?

9) Lloyd’s mirror is an alternative arrangement for demonstrating two source interference. The apparatus consists of a single slit, illuminated by plane mono-chromatic light, placed close to a mirror. Consider carefully the paths of two light rays (eg. those in the figure) and thus describe in detail the intensity of the light seen on a distant screen placed perpendicular to the mirror.

10) HRW problem 35.74.

A broad beam of monochromatic light is directed perpendicularly through two galss plates that are held together at one end to create a wedge of between them. An observer looking down on the pattern reflected from the wedge of air (which acts as a thin film) sees 4001 dark fringes along the length of the wedge. When the air between the plates is evacuated, only 4000 dark fringes are seen. Calculate, to sig significant figures, the refractive index of air from these data.