Crave the Wave, Feb 16, 2008 TEAM Mentor Invitational Score Rank

Transcription

1 Crave the Wave Mentor Invitational Feb 16, 2008 Page 1 of 15 Crave the Wave, Feb 16, 2008 TEAM Mentor Invitational Score Rank Scoring: Points will be awarded for the accuracy and quality of the responses. Show equations used to receive credit for a higher quality response. Ties will be broken using pre selected questions. 1 The sound of a lightning flash is heard 5.0 seconds after the flash. Assume that the light travels much more swiftly than the sound. Assume that the speed of sound is 330 m/s. How far away was the lightning? 2 a) What is the frequency of a second hand on an analog clock? b) What is the frequency of a minute hand on an analog clock? 3 The crowd at a football game enthusiastically creates a stadium wave. Each person stands up in turn to create a ripple effect that flows around the stadium. A) Is this an example of a transverse wave or a longitudinal wave? B) Why? 4 Ocean waves smash into a breakwater at the rate of 12 per minute. The wavelength of these waves is 39 m. What is their speed?

2 Crave the Wave Mentor Invitational Feb 16, 2008 Page 2 of 15 5 Using the diagram below a) Which letter describes the amplitude of the wave? b) Which letter represents the wavelength of the wave? c) Label a wave crest as F d) Label a wave trough as G e) What is the frequency of this wave? f) What is the period of this wave? 6 In 12 days, you can listen to the first Indians spring training game on the Tribe s Flagship station WTAM 1100 which broadcasts at 1100 KHz. What is the wavelength of the radio waves carrying the tribe games on this station? (Assume the speed of the radio waves is 3 x 10 8 m/s. ) 7 The Figure below shows an incident wave pulse moving to the left. The blue pulse encounters a mystery wave pulse from the right resulting in the superposition of the waves as shown below in red.

3 Crave the Wave Mentor Invitational Feb 16, 2008 Page 3 of 15 Make a Sketch of the mystery wave pulse travelling to the right. 8 The middle C string of a piano vibrates with a frequency of Hz when excited in its fundamental mode. What are the frequencies of the first, second, and third harmonic modes of this string? 9 a) A transverse wave is transporting energy from east to west. The particles of the medium will move in what direction(s)? b) A longitudinal wave is transporting energy from north to south. The particles of the medium will move in what direction(s)?

4 Crave the Wave Mentor Invitational Feb 16, 2008 Page 4 of A wave has amplitude of 7.5 cm and a frequency of 10 Hz, and the distance from a crest to the nearest trough (measured along the direction of the wave s energy transfer) is measured to be 5 cm. Determine the period of such a wave. 11 The drawing shows a prism and 2 light rays, A and B, both of which strike the prism perpendicularly. The prism is surrounded by an unknown liquid. When ray A reaches the hypotenuse in the drawing, it is totally internally reflected. Which one of the following statements applies to ray B when it reaches the hypotenuse? Why? A) It may or may not be totally internally reflected, depending on what the surrounding liquid is B) It is not totally internally reflected, no matter what the surrounding liquid is C) It is totally internally reflected, no matter what the surrounding liquid is. 12 A car is travelling at a speed of 90 ft/s (61 mi/hr) along a road that runs parallel to a railroad track. Practically straight in front of the car is a locomotive that is waiting for a repair. If the speed of the sound is 1080 ft/sec and the driver of the car hears a frequency of 400 Hz when the locomotive whistle is blown, what is the actual frequency of the whistle?

5 Crave the Wave Mentor Invitational Feb 16, 2008 Page 5 of An ocean wave has a wavelength of 120 m and a period of 8.77 s. A) What is the frequency of the wave? B) What is the speed of the wave? 14 A loudspeaker produces a sound wave. Does the wavelength of the sound increase, decrease, or remain the same, when the wave travels from the air into the water? Why? 15 The drawing below shows 3 layers of liquids, A, B, and C, each with a different index of refraction. Light begins in liquid A, passes into B, and eventually into C, as the ray of light in the drawing shows. The vertical lines denote the normals to the interfaces between the layers. Which liquid has the smallest index of refraction? Why?

6 Crave the Wave Mentor Invitational Feb 16, 2008 Page 6 of The frequency of electromagnetic wave A is twice that of electromagnetic wave B. For these two waves, what is the ratio! " of the wavelengths in a vacuum?! # A.! "! # = 2, because wave A has twice the speed that wave B has. B. C. D. E.! "! # = 2, because wave A has one half the speed that wave B has.! " = $, because wave A has one half the speed that wave B has.! # %! " = $, because wave A has twice the speed that wave B has.! # %! " = $, because both waves have the same speed.! # % 17 The speed of a transverse wave on a string is 600 m/s, and the wavelength is 0.24 m. The amplitude of the wave is 0.5 cm. How much time is required for a particle of the string to move through a total distance of 1.0 km? 18 The drawing shows three situations A, B, and C in which an observer and a source of electromagnetic waves are moving along the same line. In each case the source emits a wave of the same frequency. The arrows in each situation denote velocity vectors relative to the ground and have magnitudes as shown of either v or 2v. Rank the frequencies of the observed waves in descending order (largest first) according to magnitude.

7 Crave the Wave Mentor Invitational Feb 16, 2008 Page 7 of For each part of the Electromagnetic Spectrum listed below, indicate the order of the spectrum where 1 is the part of the spectrum with the lowest quantum energy and 10 is the part of the spectrum with the highest quantum energy. a.! Infrared b.! Microwaves, Radar c.! Short wave radio d.! Visible Light e.! TV and FM Radio band f.! X rays g.! AM radio h.! Gamma rays i.! Ultraviolet Light j.! Millimeter waves, telemetry 20 Suppose that a pair of flutes generates sounds waves of frequency 264 Hz and 262 Hz respectively. What is the beat frequency? 21 A swimmer is treading water (with her head above the water) at the surface of a pool 3.00 m deep. She sees a coin on the bottom directly below. a) Is the apparent depth of the coin deeper than actual depth of the coin, the same as the actual depth of the coin, or less than the actual depth of the coin? b) How deep does the coin appear to be?

8 Crave the Wave Mentor Invitational Feb 16, 2008 Page 8 of The drawing shows two sheets of polarizing material. The transmission axis of one is vertical, and that of the other makes an angle of 45 with the vertical. Unpolarized light shines on this arrangement from the left and from the right. From which direction does at least some of the light pass through both sheets? A) From the left B) From the right C) From either direction D) From neither direction 23 Name the 3 primary colors of light. 24 The sketch below shows a wave pulse on a string moving from left to right towards the end which is rigidly clamped. Sketch the wave pulse after the pulse encounters the boundary. Indicate direction of wave pulse travel with an arrow in your sketch. What is the relationship of the speed, frequency, wavelength, and amplitude of the incident wave pulse compared to the reflected pulse?

9 Crave the Wave Mentor Invitational Feb 16, 2008 Page 9 of The sketch below shows a wave pulse on a string moving from left to right towards the end which is free to move vertically. Sketch the wave pulse after the pulse encounters the boundary. Indicate direction of wave pulse travel with an arrow in your sketch. What is the relationship of the speed, frequency, wavelength, and amplitude of the incident wave pulse compared to the reflected pulse? 26 The figure shows a light ray striking a glass prism (n = 1.5). Explain/Draw the result of the ray striking the edge of the prism as shown.

10 Crave the Wave Mentor Invitational Feb 16, 2008 Page 10 of The sketch below is a snapshot of an incident wave on a string travelling from left to right from a low density string to a higher density string. Sketch what happens after the pulse encounters the boundary between the low and high density regions. 28 The sketch below is a snapshot of an incident wave on a string travelling from left to right from a higher density string to a lower density string. Sketch what happens after the pulse encounters the boundary between the high and low density regions.

11 Crave the Wave Mentor Invitational Feb 16, 2008 Page 11 of A person is viewing a ball through a Cyan filter. The ball appears to be green. The same ball is viewed with a magenta filter and now appears to be black. What color is the ball when revealed with white light? 30 What colors of light combine to make A) Yellow? B) Magenta? C) Cyan? 31 Two automobiles heading in opposite directions approach each other, the first at 88 ft/s and the second at 66 ft/s. The driver of the first sounds a horn having a frequency of 400 Hz. A) What frequency does the driver of the second car hear? (Assume speed of sound to be 1100 ft/s). B) After the automobiles have passed each other what frequency does the drive of the second car hear? 32 Red light (! &664 nm in vacuum' is used in Young s experiment with the slits separated by a distance ( &1.20 * 10 +, m. The screen is located at a distance of L = 2.75 m from the slits. Find the distance, y, on the screen between the central bright fringe and the third order bright fringe.

12 Crave the Wave Mentor Invitational Feb 16, 2008 Page 12 of A cross sectional view of the eye is shown below: Light entering the eye is shown in the diagram as rays. The picture demonstrates that a person with myopia (near sightedness) will see a blurry image because the light is focused in front of the retina and not on the retina. A) What type of corrective lens will correct the problem? B) Why? C) Sketch the corrected light ray path. 34 When a fish looks up at the surface of a perfectly smooth lake, the surface appears dark except inside a circular area directly above it. A) What optical phenomenon causes the rest of the surface to appear black? B) Calculate the angle defining the illuminated region denoted by angle C in the picture below

13 Crave the Wave Mentor Invitational Feb 16, 2008 Page 13 of a) When light passes from a more optically dense medium into a less optically dense medium, will it bend towards or away from the normal? b) When light passes from a medium with a lower index of refraction into a medium with a higher index of refraction, will it bend towards or away from the normal? c) When light passes from a medium where the speed of light is slower into a medium where the speed of light is faster, will it bend towards or away from the normal? 36 a) What are the regions of high pressure called in a sound wave? b) What are the regions of low pressure called in a sound wave? 37 Two astronauts are 1.5 m apart in their spaceship. One speaks to the other. The conversation is transmitted to earth via electromagnetic waves. The time it takes for sound waves to travel at 343 m/s through the air between the astronauts equals the time it takes for the electromagnetic waves to travel to earth. How far away from the earth is the spaceship? 38 At what angle of incidence should a beam of light strike the surface of a still pond if the angle between the reflected ray and the refracted ray be 90? (n = 1.33 for water).

14 Crave the Wave Mentor Invitational Feb 16, 2008 Page 14 of The sun is million km from the earth. a) How long does it take light from the sun to reach earth? b) How long does it take sound to reach earth? 40 One method of determining the refractive index of a transparent solid is to measure the critical angle when the solid is in air. If -. is found to be 38, what is the index of refraction of the solid? 41 A fish in a still pond is observing the sunset. When the sun is setting and is at the horizon, where does the fish perceive the sun to be? Give your answer in degrees from the horizontal. The index of refraction for water is Sound waves with a frequency of 320 Hz are sent into the top of a vertical tube containing water at a level that can be adjusted. If standing waves are produced at two successive water levels: 20 cm and 73 cm. What is the speed of the sound waves in the air of the tube?

15 Crave the Wave Mentor Invitational Feb 16, 2008 Page 15 of A 40 cm long brass rod (cylindrical and hollow and open at both ends) is dropped one end first onto a hard floor but is caught before it topples over. The resulting tone is measured by an oscilloscope and is determined to have a frequency of 3 khz. What is the speed of sound in brass? 44 A hunter is standing on the flat ground between two vertical cliffs that are directly opposite each other. He is closer to one cliff than to the other. He fires a gun and, after a while, hears three echoes. The second arrives 1.6 s after the first, and the 3 rd arrives 1.1 s after the second. Assuming the speed of sound is 343 m/s and that there are no reflections from the ground, find the distance between the cliffs. 45 TRUE or FALSE: a) The speed of sound in air is greater in warm air than in cool air. b) The speed of sound along a guitar string is greater on a thicker string than on a thinner string given that both strings are the same length and are under the same tension. c) In general, sound travels slowest in gases, faster in solids, and fastest in liquids