Optical Engineer___________________________ Research Period _______ CHAPTER 27 #1 YOU LIGHT UP MY LIFE 1. Assume that the sun is 1.5 x 108 km from the earth. Calculate the time required for light to travel from the sun to the earth. (8 min. 20 s) Watch the units! 2. A radar signal is reflected from the moon. It is detected after a 2.58 s time lapse between sending and receiving. How far away in kilometers is the moon? (3.9 x 105) 3. What is the frequency of a microwave that has a wavelength of 3.0 cm (don’t forget to convert to meters)? (1.0 x 1010 Hz) 4. Convert 700 nm, the wavelength of red light, to meters. Express in scientific notation. 5. Radio stations are usually identified by their frequency. One radio station in the middle of the FM band has a frequency of 99.0 MHz. What is its wavelength? (3.03 meters) 6 (1). Which theory of light is the photon more consistent with- the wave theory or the particle theory? 7 (4). How long does light take to travel from the sun to Earth? From the star Alpha Centauri to Earth? 8 (5). How long does light take to travel a distance of one light-year? 9 (6). What is the source of electromagnetic waves? 10 (8). How do the frequencies of infrared, visible, and ultraviolet light compare? 11 (10). Different bells and tuning forks have their own natural vibrations, and emit their own tones when struck. How is this analogous to atoms, molecules and light? 12 (11). Light incident upon a pane of glass slows down in passing through the glass. Does it emerge at a slower speed or at its initial speed? Explain. 13 (12). Will glass be transparent to frequencies of light that match its own natural frequencies? 14 (13). Does the time delay between the absorption and reemission of light affect the average speed of light in a material? Explain. 15 (17). Why are metals shiny in appearance? 16 (19). a. Distinguish between a solar eclipse and a lunar eclipse. b. Which type of eclipse is dangerous to your eyes if viewed directly? 17 (24). What evidence can you cite to support the idea that light can travel through a vacuum? 18 (28). You can get a sunburn on a sunny day and on an overcast day. But you cannot get a sunburn if you are behind glass. Explain. 19 (29). Pretend a person can walk only at a certain pace-no faster, no slower. If you time her uninterrupted walk across a room of known length, you can calculate her walking speed, If, however, she stops momentarily along the way to greet others in the room, the extra time spent in her brief interactions gives an average speed across the room that is less than her walking speed. How is this like light passing through glass? In what way is it not? 20 (30). If you fire a ball through a pile of sand, it will slow down in the sand and emerge at less than its initial speed. But when light shines on a pane of glass, even though it slows down inside, its speed upon emerging is the same as its initial speed. Explain why. 21 (31). Short wave lengths of visible light interact more frequently with the atoms in glass than do longer wavelengths. Which do you suppose takes the longer time to get through glass: red light or blue light? 22 (32). Suppose that sunlight is incident upon both a pair of reading glasses and a pair of sunglasses. Which pair would you expect to be warmer, and why? 23 (33). Why does a high-flying plane cast little or no shadow on the ground while a low-flying plane casts a sharp shadow? Optical Engineer___________________________ Research Period _______ CHAPTER 27 #2 We're Polar(ized) opposites 1 (20). What is the difference between light that is polarized and light that is not? 2 (21). Why is light from a common lamp or from a candle flame non-polarized? 3 (22). In what direction is the polarization of the glare that reflects from a horizontal surface? 4 (23). How do polarizing filters allow each eye to see separate images in the projection of three-dimensional slides or movies? 5 (34). Why do Polaroid sunglasses reduce glare, whereas unpolarized sunglasses simply cut down on the total amount of light reaching our eyes? 6 (35). An ideal polarizing filter transmits 50% of the incident nonpolarized light. Why is this so? 7 (36). What percentage of light would be transmitted by two ideal polarizing filters, one atop the other, with their axes aligned and parallel? What percentage would be transmitted if their axes are crossed at right angles?