Name: Answer Key Date: Regents Physics. Waves

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1 Nae: Answer Key Date: Regents Physics Test # 13 Review Waves 1. Use GUESS ethod and indicate all vector directions. 2. Ters to know: echanical wave, transverse wave, longitudinal wave, surace wave, electroagnetic wave, pulse, ediu, cycle, crest, trough, equilibriu position, traveling wave, period, requency,, aplitude, phase, principle o superposition, constructive intererence, destructive intererence, node, antinode, standing wave, resonance, diraction, pitch, volue (loudness), Doppler shit. 3. What is the dierence between a transverse and a longitudinal wave? Draw a picture o each. Give an exaple o each. Transverse disturbance perpendicular to wave otion Longitudinal disturbance parallel to wave otion 4. What is the dierence between a traveling wave and a standing wave? What are the conditions necessary to produce a standing wave? Traveling wave oves along the ediu Standing wave appears to stand still need a wave to relect o o a ixed point 5. What is the dierence between a echanical wave and an electroagnetic wave? Give an exaple o each. Mechanical wave disturbance that travels through a ediu Electroagnetic oscillations o electric charges no ediu necessary 6. Sketch two pulses that will interere constructively. Sketch two pulses that will interere destructively. 7. How can you change the speed o a wave in a rope? How can you change the requency? How can you change the aplitude? How can you change the?. When a wave crosses a boundary ro one ediu to another (say, ro air to water or ro a thick spring to a light spring) what characteristic o the wave reains the sae? The requency stays the sae. It s the, speed and aplitude that change 9. Sketch a picture o each o the ollowing wave phenoena: relection, diraction, intererence. 10. As a car honking its horn approaches you standing on a street corner, what do you notice about the requency, aplitude and o the sound o the horn? What do you notice about these things as the car passes you and travels away? What is the nae or this phenoenon? Doppler eect Toward you higher requency, saller, no change in aplitude Away ro you lower requency, larger, no change in aplitude 11. Sketch one cycle o a standing wave and label the nodes and antinodes. Sketch one-hal cycle. Sketch 1 ½ cycles. 12. As the pitch o a sound increases, what happens to its requency? As the loudness o a sound increases, what happens to its aplitude? Increasing pitch eans an increase in requency Increasing sound eans an increase in aplitude 13. Which two actors will result in a wave diracting ore: narrow opening or wide opening? Sall or large? A narrow opening is harder or a wave to squeeze through, diracts ore A large has a hard tie squeezing through an opening, diracts ore 232

2 Directions: Read each question careully and record your answers in the space provided. Be sure to show all work! Answers should be in signiicant igures. You will be graded on proper use o the GUESS ethod. I the GUESS ethod is not appropriate, show all work to receive partial credit. These will be the sae directions on the test. Practice the GUESS ethod now. Use the wave to answer questions 1-6. Length o one wave 1. What is the o the wave? 2. What is the aplitude o the wave? 4 Height o crest or trough 3. Over tie, particle A will ove in which direction? Up until the crest and then down I a student observes 60.0 waves passing in 12 seconds: 4. What is the requency o the wave? # waves 60.0 waves 5.0 Hz tie 12s aplitude 5. What is the period? T s 5.0 Hz 6. What is the velocity o the wave? v(5.0 Hz )( ) 40 right s Velocity needs direction Use the waves below to answer questions Two waves, A and B, are shown below. They are traveling in the sae ediu at the sae tie. Both have the sae but dierent aplitudes. 7. In the space below, show the resultant wave i A and B interere. aplitude. What is the o wave A?.0 9. What is the aplitude o wave B? 2.0 To draw the resultant wave, add the aplitude at each spot, ark it, and draw the wave 10. What is the o the cobined wave? What is the aplitude o the cobined wave? What type o intererence is this? Destructive The waves are out o phase, when added together they create a saller wave 233

3 13. What is the o the ollowing waves? Wave A Wave B Wave A = 4.0 Wave B = A student observes 50. waves passing in 10. seconds. a. What is the requency o the wave? # waves 50. waves 5.0 Hz tie 10. s b. What is the period o the wave? T s 5.0 Hz c. I the is 1.5 eters, what is the velocity o the wave? v (5.0 Hz )(1.5 ) 7.5 s orward Velocity needs direction 15. What is the requency o a 3.0 eter wave traveling at 100. /s? 100 v s 33Hz I the requency o a wave doubles, while the speed reains constant, what happens to the? v 1 Hal What is the requency o a light whose is: a. 6.7 x 10-7? b. 5.9 x 10-7? v s Hz v s Hz What is the o a light wave whose requency is 3 x Hz. v A sound wave has a requency o 292 Hz. a. Calculate the o the wave. s v 331 s Hz 110 a. How long will it take or the wave to travel 25? t d s v 331 s 6 The speed o light is listed on the ront cover o the reerence tables. The speed o light is listed on the ront cover o the reerence tables. The speed o sound is listed on the ront cover o the reerence tables. Sound waves travel at constant speed in the sae ediu. 234

4 b. What is the period o the wave? T s 292Hz 20. Which phenoenon does not occur when a sound wave reaches the boundary between air and a steel block? (A) relection (B) polarization (C) absorption (D) reraction 21. As a periodic wave travels ro one ediu to another, which pair o the wave s characteristics cannot change? (A) period and aplitude (B) period and requency (C) aplitude and (D) requency and velocity 22. The distance ro the Moon to Earth is 3.9 x 10 eters. What is the tie required or a light ray to travel ro the Moon to Earth? (A) 0.65 s (B) 3.9 s (C) 1.3 s (D) 2.6 s 23. The diagra below shows a transverse wave oving to the right along a rope. Light waves can be polarized, sound waves cannot. Frequency does not change with a ediu change, and period is the reciprocal o requency The speed o light is listed on the ront cover o the reerence tables. t d v s As the wave passes point X, the otion o x will be (A) let, then right (B) up, then down (C) in a circle (D) down, then up 24. Two waves have the sae requency. Which wave characteristic ust also be identical or both waves? (A) intensity (B) phase (C) aplitude (D) period 25. How any nodes are represented in the standing wave diagra below? The trough hits irst so it will ove down, then the crest coes so it oves up. Period is the reciprocal o the requency Nodes the points o iniu displaceent (A) 6 (B) 4 (C) 3 (D) The requency o a light wave is 5.0 x hertz. What is the period o the wave? (A) 6.0 x 10 7 s (B) 5.0 x s (C) 2.0 x s (D) 1.7 x 10 6 s 1 1 T Hz 27. An astronoer on Earth studying light coing ro a star notes that the observed light requencies are lower than the actual eitted requencies. The astronoer concludes that the distance between the star and Earth is (A) increasing (B) not changing (C) decreasing 235 Doppler Eect As the star oves away the increases so the requency decreases

5 2. The diagra below shows two pulses, each o length λ, traveling toward each other at equal speed in a rope. The crests line up with troughs and cancel Which diagra best represents the shape o the rope when both pulses are in region AB? 29. What is the o a 30. hertz period wave oving at 60. eters per second? (A) 1,00 (B) 2.0 (C) 20. (D) The driver o a car sounds the horn while traveling toward a stationary person. Copared to the sound o the horn heard by the driver, the sound heard by the stationary person has (A) higher pitch and longer (B) lower pitch and shorter (C) lower pitch and longer (D) higher pitch and shorter 31. When an opera singer hits a high-pitch note, a glass on the opposite side o the opera hall shatters. Which stateent best explains this phenoenon? (A) The singer and the glass are separated by an integral nuber o s. (B) The requency o the note and natural vibration requency o the glass are equal. (C) The vibrations o the note are polarized by the shape o the opera hall. (D) The aplitude o the note increases beore it reaches the glass. 32. The periodic wave in the diagra below has a requency o 40. hertz. Doppler Eect As the sounds oves toward the decreases so the requency increases so the pitch increases v 60. s 30.Hz This is resonance length #wave 2 v (40.Hz)(1.5) What is the speed o the wave? (A) 13 /s (B) 120 /s (C) 60. /s (D) 27 /s 33. What is the angle between the direction o propagation o a transverse wave and the direction in which the aplitude o the wave is easured? (A) 90 0 (B) 10 0 (C) 45 0 (D) 0 0 Transverse wave the particles vibrate perpendicular to the wave otion 236

6 Answers: up 4. 5 Hz s /s 7. see sheet Destructive 13. A = 4, B = a. 5.0 Hz b s c. 7.5 /s orward Hz 16. cut in ½ a. 4.5 x Hz b. 5.1 x Hz x a b s 20. B 20. B c s 21. C 22. D 23. D 24. B 25. C 26. A 27. C 2. B 29. D 30. B 31. C 32. A 33. B 34. B 35. A 36. C 37. B 3. B 34. In the diagra below, the distance between points A and B on a wave is 0.10 eter. A and B are hal a wave apart This wave ust have (A) a o 0.10 (B) a o 0.20 (C) an aplitude o 0.20 (D) an aplitude o Light is to brightness as sound is to This is the aplitude o the waves (A) period (B) loudness (C) speed (D) color 36. What is the period o a periodic wave that has a requency o 60. hertz? (A) 1.7 x 10-2 s (B) 3.3 x 10 2 s (C) 2.0 x 10 4 s (D) 3.0 x 10-3 s T Hz 37. A onochroatic bea o light has a requency o 6.5 x hertz. What color is this light? (A) orange (B) yellow (C) blue (D) violet 3. A periodic wave travels through a rope, as shown in the diagra below. Waves only transer energy ro location to location Use the requency to look up the color on the EM spectru on the reerence tables. As the wave travels, what is transerred between points A and B? (A) neither ass nor energy (B) energy, only (C) both ass and energy (D) ass, only 39. The distance between successive antinodes in the standing wave pattern shown below is equal to Antinode to antinode is crest to crest, which is hal a wave. (A) 2 (B) 1/2 (C) 1/3 (D) 1 237

Practice Problems For 1st Wave Exam

Practice Problems For 1st Wave Exam For 1st Wave Exam 1. Which wave diagram has both wavelength ( ) and amplitude (A) labeled correctly? A) B) C) 5. The energy of a sound wave is most closely related to the wave's A) frequency B) amplitude