Index of Refraction - Physics - Past Paper, Exams of Physics

Download Index of Refraction - Physics - Past Paper and more Exams Physics in PDF only on Docsity! Physics 152 Roster No.: Due: Wednesday, November 23, 2005 Score: Take-Home Midterm Exam #3, Part A NO exam time limit. Calculator required. All books and notes allowed, and you may obtain help from others. Complete all of Part A AND Part B. For multiple-choice questions, circle the letter of the one best answer (unless more than one answer is asked for). For fill-in-the-blank and multiple-choice questions, do you NOT need to show your work. Show your work on all free-response questions. Be sure to use proper units and significant figures in your final answers. Ignore friction/air resistance, gravity, and relativistic effects in all problems, unless told otherwise. Assume that all lenses and mirrors are ideally “thin” unless told otherwise. Physical Constants: c = 2.998 × 108 m/s Conversions: It’s an open-book test, so you can look them up! 1. (4 pts.) Convert the following quantities into the given units. Fill in the blanks. (You do NOT need to show your work.) Use scientific notation where appropriate (very large or very small values), and express all final values to 2 significant figures. a. 4.5 × 10–5 THz = kHz b. 3.0 × 1011 cm/s = mi/h (miles/hour) c. 1.5 × 108 km/h = ly/century (1 ly = 1 light-year = distance that light travels in one year in vacuum) d. 550 nm = Å (angstroms) 2. (4 pts.) TRUE or FALSE (T or F): ______ Yellow light travels faster than green light in vacuum. ______ Yellow light has a higher frequency than green light in vacuum. ______ Ultraviolet light has a shorter wavelength than microwaves do. ______ Electromagnetic waves are “transverse” waves. ______ As light passes from air into glass, its frequency does not change. ______ As light passes from glass into air, its wavelength shortens. ______ The focal length of a lens depends on both (1) the material from which the lens is made, and (2) the curvature of its sides. ______ The focal length of a mirror depends on both (1) the height of the mirror, and (2) the mirror’s radius of curvature. 3. (1 pt.) The index of refraction of liquid water is 1.33, while the index of ice is 1.29. Therefore, the speed of light in liquid water is __________ the speed of light in ice. A. 3% faster than D. 3% slower than B. 4% faster than E. 4% slower than G. the same as C. 5% faster than F. 5% slower than 4. (1 pt.) Suppose that a particular type of glass is advertised as being non-dispersive. This type of glass could be used successfully in the manufacture of all of the following EXCEPT which one? A. a converging lens B. a diverging lens C. a transmission diffraction grating D. a prism used to spread incoming light into a spectrum 5. A beam of initially unpolarized light first passes through polarizer A, then through polarizer B. Polarizer B can be rotated so that its axis forms an angle between 0˚ and 90˚ to the axis of polarizer A. (You do NOT need to show your work.) a. (1 pt.) What fraction of the intensity of the initial unpolarized light is transmitted through polarizer A? _______ b. (2 pts.) Let I1 be the intensity of plane-polarized light that passes through A and is incident on B. If only 15% of I1 is transmitted through B, what is the angle between the axes of the two polarizers? __________ 6. (2 pts.) Suppose that nair = 1.00 and nwater = 1.33. Reflected sunlight is 100% polarized when it is reflected from a puddle at what angle? __________ 7. a. (2 pts.) At what distance d0 from a converging lens (focal length = 25 cm) should you place an object so that its image has a magnification of exactly –1? __________ b. (2 pts.) At what distance di from the lens will the image in part (a) be located? __________ c. (1 pt.) The image in part (a) will be located: A. on the same side of the lens as the object B. on the opposite side of the lens from the object d. (1 pt.) The image in part (a) is... A. upright and real C. inverted and real B. upright and virtual D. inverted and virtual 3. You are using a magnifying glass to view a 1.0-cm-tall insect. The lens has focal length f = 4.0 cm, and the insect is 2.5 cm away from the lens. a. (4 pts.) What is the magnification of the insect’s image? b. (1 pt.) The image of the insect in part (a) is… A. real and upright B. virtual and upright C. real and inverted D. virtual and inverted c. (2 pts.) Carefully sketch the above situation to scale: each square = 1 cm on a side. Draw and label an object and an image, to scale. Draw all 3 principal rays in your sketch. d. (2 pts.) If you wanted to use the same lens to focus the Sun’s rays to burn a hole in a sheet of paper (or in the insect, if you’re feeling cruel), how far should you hold the lens from the paper? (Hint: assume the Sun is infinitely far away, so that rays of sunlight are parallel as they reach the lens.) Justify your answer either with a simple sketch or with a formula. f f scale: 1 cm/div. 4. (5 pts.) A ray of light, initially horizontal, passes through a cylinder of glass of radius R, as shown. Assume that nair = 1.00. Based on the geometry of the ray’s path as shown, find: a. the final angle of the ray, θ f, with respect to the horizontal b. index of refraction of the glass, nglass 45˚ nair = 1.00 nglass = ? R R R θf = ? horizontal ray