4. Light of a certain wavelength will reflect off of the top (1) and bottom (2) surfaces of a butterfly scale to constructively interfere. However, light can also reflect off the top surface of the next consecutive scale (3), and cause constructive interference for other wavelengths of light (this is why butterfly scales seem to made up of a mixture of many different colors). In the diagram to the right all these paths are straight up and down. The index of refraction of the butterfly scale is 1.6. Between which of the following two paths will the constant phase difference, Ao, be n radians? eye 1 2 3 n=1.0 n=1.6 130nm n=1.0 200nm a. Between paths (1) and (2). b. Between paths (2) and (3). c. Between paths (1) and (3). d. All of the above path differences lead to a t phase shift. e. Only choices a) and b) above will lead to a t phase shift.

As shown the viewing screen in a double-slit experiment with monochromatic light. Fringe C is the central maximum.a. What will happen to the fringe spacing if the wavelength of the light is decreased?b. What will happen to the fringe spacing if the spacing between the slits is decreased?c. What will happen to the fringe spacing if the distance to the screen is decreased?d. Suppose the wavelength of the light is 500 nm. How much farther is it from the dot on the screen in the center of fringe E to the left slit than it is from the dot to the right slit?

Q1. The air in a dark, smoky room often looks bluish when illuminated by white light. What creates this bluish appearance? (clue, Rayleigh scattering) Q2. A diamond pendant sparkles with color when you look at it in sunlight. From where do the colors come. (clue, dispersion) Q3. A thin layer of oil or gasoline floating on water appears brightly colored in sunlight. From where do the colors come (clue, Interference)

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