Waves ~ Learning Guide Name: Instructions: Using a pencil, answer the following questions. The Pre-Reading is marked, based on effort, completeness, and neatness (not accuracy). The rest of the assignment is marked, based on effort, completeness, neatness, and accuracy. Every time you see a bold word, make sure you refer back to your "Submission Requirements." Do your best! Pre-Unit Thoughts: How does the sound of a stereo on the other side of the room get to your ear? Unit Notes & Practice: 1. You are using a crowd of people to simulate the transfer of energy from one side of the room to another. Provide instructions to each individual as to how to act to properly simulate the following wave types: a) Longitudinal Waves: b) Transverse Waves: Page 1 of 11
2. A skipper on a boat notices wave crests passing the anchor chain every 5 seconds. The skipper estimates the wave height to be 1 m (above calm water) and the distance between crests at 15 m. What are the characteristics of the waves? Show work and include units. a) amplitude = b) speed = c) frequency = d) period = 3. The distance light travels in one year is called a light year. How many kilometres are there in one light year? Show your work. (ans. 9.5 x 10 12 km) 4. An imaginary star is four light years from earth. The star has a planet, upon which a large mirror has been installed. The mirror faces earth. A ten-year-old boy aims his telescope at the mirror. How old will the boy be when he sees his own image reflected back at him? How old will he look in the mirror? Justify. Page 2 of 11
5. Complete the table below with descriptive comments. You may have to do some Internet searching to complete all the cells: Water Sound Light Medium Vibration Direction on top, & below Facts about Speed Facts about Period / Frequency Facts about Amplitude (include units) Effect when you move towards or away source. Frequencies below those you can sense (include examples of use). Frequencies above those you can sense (include examples of use). Some terms that should be included in your descriptions above (not in any order): surface, longitudinal, transverse, water, air, no medium, wind, rock, pitch, loudness, 3 x 10 8 m/s, 340 m/s, varies, EM, Doppler, red/blue-shift, c, Infra red, X-rays, ultrasonic, bats, infrasound, elephants, brightness, m, decibels, lumens, Page 3 of 11
6. Compare and contrast the Doppler effect and Blue/Red-Shift. 7. Using diagrams and comments to explain the creation of a sonic boom. 8. Can a bomb make a sonic boom? Justify your answer. Page 4 of 11
9. When timing a 100m run, officials at the finish line are instructed to start their stopwatch at the sight of smoke from the starter's pistol rather than the sound of the pistol's firing. What would be the difference in time if they used sound? 10. Herds of African elephants are generally spread over large areas. Infrasonic sound waves (sound waves below the human range of frequency detection) are used by these elephants to locate each other and to communicate. Sound waves with low frequencies have a greater ability to bend around obstacles and generally carry further. Scientists have detected sound waves with frequencies as low as 13 Hz being produced by elephants. Assuming a speed of sound of 350 m/s, determine the wavelength of these sounds waves. Show your work. (ans. 27 m) 11. Students went hiking in a canyon let out a holler which reflected off a nearby rocky cliff and was detected as an echo 1.80 seconds later. Determine the distance to the rocky cliffs. Assume a speed of sound of 344 m/s. Show your work. (ans. 310 m) Page 5 of 11
12. Shown below are six waves, which are all the same kind of wave (e.g., all seismic waves) traveling in various media. The waves all have the same frequency, but their amplitudes, A, and wavelengths, l, vary as shown in the figures. Specific values for these properties are given in each figure. Rank these waves from greatest to least based on the speed of the waves. That is, put first the wave that is moving fastest and put last the wave that is moving slowest. Fastest 1 2 3 4 5 6 7 8 Slowest Carefully explain the reasoning behind your ranking. How sure were you of your ranking? (circle one) Basically Guessed Sure Very Sure 1 2 3 4 5 6 7 8 9 10 Page 6 of 11
11. A dog wags its tail 50 times in 20 s. What are (a) the frequency and (b) the period of vibration of the tail? Show your work. (ans. 2.5 Hz, 0.40 s) f = T= 12. If the speed of sound is 330 m/s, what wavelength does a sound of frequency 512 Hz have? Show your work. (ans. 0.65 m) 13. Please complete these diagrams showing all waves, to show what happens to waves after they encounter the barrier or other obstacle. Also, name the phenomenon that occurs in each situation (refraction, diffraction, interference, or reflection). Page 7 of 11
15. You are 1.6 m tall. What is the shortest wall mirror you need to see your whole body, while standing, in the mirror? Draw ray diagrams from the top of your head to your eye, and from the bottom of your feet to your eye. 16. At what speed would light travel in a glass with an index of refraction of 2.0? Show your work. (ans. 1.5 x 10 8 m/s) 17. A beam of light makes an angle of 35 o with the normal as it approaches a flat glass block. If the index of refraction of the glass is 1.60, at what angle will the refracted beam enter the glass, relative to the normal? Draw ray diagrams to demonstrate your answer. (ans. 21 degrees) Page 8 of 11
18. Explain a way to remember how light bends when going from a slower medium to a faster and visa versa. Use diagrams and explanations. 19. The fact that light can be polarized indicates that light can be treated as a wave or particle? Justify your answer. 20. If you can see someone in a mirror, they can see you. Is this true? Demonstrate your conclusion using ray diagrams and comments. 21. The closer your had is to a light source the bigger the shadow. Is this true? Demonstrate your conclusion using ray diagrams and comments. Page 9 of 11
22. Draw ray diagrams to explain why we call a concave mirror a converging mirror and a convex mirror a diverging mirror. Start with parallel rays approaching the mirrors. 23. Draw the ray diagram on the concave mirror situation below to determine the position of the resulting image. Using your result, determine if the image is real or virtual, supporting your answer. 24. Draw the ray diagram on the picture below to determine the position of the resulting image. Using your result, determine if the image is real or virtual, supporting your answer. Is the image Real or Virtual? Support your answer. Page 10 of 11
25. When using a magnifying glass close to the eye, an image may be seen clearly if it is located between the near point and far point of the eye. Consider looking through the lens at an object held in your hand. Most people bring the hand closer (and the image comes closer as well) until the image is at the near point of the eye. Bringing it even closer makes it "out of focus". There's a significant change in the image size, the image being larger as it is brought closer. Your brain easily senses this, and, desiring to see more detail, guides the hand holding the object to a position that makes the image as large as possible. Using ray diagrams and descriptions, show and explain the situations mentioned above. Page 11 of 11