p235w11_practice_exam_3_2_sol

# To form images a surface must reflect light but it

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Unformatted text preview: so be smooth on the scale of the wavelength of light; 500 nm or so. Most surfaces are quite rough on this scale, and reflect light diffusely (in every direction) instead of specularly (only with an angle of reflection equal to the angle of incidence). When reflections are diffuse, they do not form images, because there is no way to tell where reflected light originally came from. 4: (10 points) Consider an object made of three parts, labeled A, B, and C, as shown. Light from this object encounters a diverging lens, which has a focal length f (the focal points are shown). The object is located a distance 2f to the left of the lens. a: (3) Use ray tracing to find the location of the image of the point labeled A on the object for this converging lens. Show all three principal rays as carefully as you can. A B C b: (3) Now draw the location of the image of point C. You need not show the rays, just label the image location as accurately as you can A B C C’ c: (4) Imagine that you add a second lens to the system. This time it is a converging lens, with the same focal length f. This second lens is placed so that its focal point coincides with the focal point of the diverging lens. Where does the final image form? A B C Image from the first lens: 1 1 1 2 f DI f or DI This is the object for the second lens, so for this: 3 1 1 8f or DI 8 f DI 5 f 2f 3 5: (10 points) Consider the famous Rosalind Franklin x-ray diffraction picture which led to the discovery of the structure of DNA. The picture is reproduced below. a: (2 points) If the looping repetitions of...
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