Unit 10 Waves Review Section 1: Know the definitions and/or concepts of the following:

Transcription

1 Name Date Period Unit 10 Waves Review Section 1: Know the definitions and/or concepts of the following: diffraction: frequency: reflection: longitudinal wave: refraction: transverse wave: amplitude: electromagnetic wave: wavelength: mechanical wave: period: Crest: Trough: Doppler Effect: Red Shift: Blue Shift: Section 2: Complete the following. Each involves an understanding of the physics principles discussed in this unit. 1) A vibrating membrane can produce a sound wave through air. If the membrane vibrates five times quicker than it starts out at, a) By how much does the wavelength of the sound wave change? b) By how much does the period of the sound wave change? 2) A 60 Hz and a 900 Hz sound wave traveling through air are compared. a) How does the wavelength of the 60 Hz sound wave compare to the wavelength of the 900 Hz sound wave? (longer, shorter, the same) b) Which of the two sound waves will travel faster through air? 1

2 3) Which travels fastest through empty space, radio waves, visible light waves or gamma rays? 4) An experiment was performed to measure the wavelength of sound waves when the frequency is known. Then an experiment was performed to measure the wavespeed of each of the frequencies of sound waves. The data for both of these experiments is shown below. Wavelength (meters) Frequency (Hz) Wavespeed (m/s) a) From the data collected what type of a relationship, if any, is there between wavelength and frequency? (direct, inverse, quadratic, no relationship.) b) From the data collected what type of a relationship, if any, is there between wavespeed and frequency? (direct, inverse, quadratic, no relationship.) 5) Paul Buenorico, a foolish want-to-be helioseismologist, detects that close images of the Sun reveals that there are many small (size of US States) light and dark spots on the surface. He further concludes that the light from the light spots is shifted to smaller wavelengths (blueshifted) and the light from the dark spots is shifted to larger wavelengths (redshifted). Explain what these shifts mean about the motion of the light and dark material. 6) If you were standing on the side of a road and an ambulance was approaching you with its sirens on, how would the frequency of the siren compare if the ambulance was stationary? 7) Two wavelengths of electromagnetic radiation are compared. One with a wavelength of 1 km and the other with a wavelength of 1 nm. a) Which of the two wavelengths will have the larger frequency? b) Which of the two wavelength will have the lower energy? 8) A student is examining two lasers, one red light and the other is green. The frequency of the red light is less than the frequency of the green light. a) Which of the two lasers emit electromagnetic radiation with the shortest wavelength? b) Which of the two emits electromagnetic radiation with the higher energy waves? 2

3 9) Several situations are listed below. Label each one according to the one wave property that is being described (reflection, refraction, diffraction or Doppler Effect.) a) A ring is seen at the bottom of a small pond filled with water but when you reach in to get it the ring is deeper than you expected. b) In a wide-open field, you can hear your friend s voice as he/she speaks when your friend is facing away from you. c) You are trying to study in your room when you sibling turns on music in the next room. Your door is cracked open but you can hear the sound from the stereo as if the door is wide open. d) Your friend is wearing glasses and then takes them off. You notice that your friend s eyes look smaller when he/she is wearing the glasses. e) An astronomer notices that the light of a nearby star is shifted to higher frequencies and concludes that the star must be moving toward her line of sight. f) A firecracker is ignited and shortly after you hear the boom again coming from the direction of a nearby building. Section 3: Work through each of the following problems. Show your work and include units on all solutions. 1) The electromagnetic radiation of a certain red laser has a wavelength of 670 nm. Note: (1 nm = 10-9 m) a) Find the frequency associated with this wavelength. b) Find the energy associated with this wavelength. 2) Find the frequency in megahertz of a 1.5 m radio wave. (1 MHz = 10 6 Hz) 3) A sound wave traveling at 343 m/s has a wavelength of 24.5 meters. Calculate the frequency of this sound wave. 4) The highest frequency most humans can hear is 20,000 Hz. a) Calculate the wavelength associated with this frequency for sound that travels at 343 m/s. b) Find the period of this sound wave. 3

4 5) Find the speed of a wave, in m/s, that has a wavelength of 7.45 meters and a frequency of 11.3 Hz. 6) Calculate the speed of waves in a pond that are 0.25 meters apart and made by tapping the water surface eight times each second. 7) The echo of a certain type of bat is 100,000 Hz. If this reflected sound from the rock is heard 0.8 sec after the bat makes his sound, a) Find the distance to the rock from the bat (assume the bat is at rest). b) Find the wavelength of the bat s sound. (Hint: The sound wave is traveling through air.) (Use this information to answer problems 8-14) An elastic rope is stretched horizontally 18 meters. One end of the rope is attached to a wall and the other end is vibrated at difference frequencies to produce standing waves. For each standing wave 10 periods are measured using a stopwatch. 8) Calculate one period, the frequency and the wavelength for each standing wave and record the values in Table 1. Standing Wave Table 1 10 Periods (seconds) One Period (seconds) Frequency (Hz) Wavelength (meters) A 3.4 B 2.6 C 2.1 D 1.8 4

5 9) Use the data from Table 1 to make a wavelength (y) vs. period (x) graph. Set scales and label axes ) Based on your data and your graph, is the relationship between period and wavelength direct, inverse, or is there no relationship? 11) Draw in a best fit line through your data on the Wavelength vs. Period graph. The slope of this graph is equal to the wave speed through the elastic rope. Find the slope of the graph and record the value below. (Include proper units.) 12) If another standing wave was produced using the rope but this time the wave had 2 nodes from end to end, calculate the wavelength in meters. 13) If another standing wave was produced using the rope but this time the wave had 2 nodes from end to end, calculate the frequency of the wave in Hertz. 14) If another standing wave was produced using the rope but this time the wave had 2 nodes from end to end, calculate the period of the wave in seconds. 5