Waves Wave Characteristics

Transcription

1 Name: Date: Waves 4.4 Wave Characteristics. A transverse travelling wave has amplitude A 0 and wavelength λ. The distance between a crest and its neighbouring trough, measured in the direction of energy transfer of the wave is equal to A. A 0. B. A 0. C. λ. D. λ.. The graph below shows the variation of air pressure with distance along a wave at one given time. The arrow indicates the direction of travel of the wave. air pressure + normal air pressure P distance along wave The air pressure at point P is A. increasing. B. decreasing. C. constant. D. zero.

2 3. The diagrams below show two standing wave patterns that are set up in a stretched string fixed at both ends. The frequency of pattern is f and that of pattern is f. pattern frequency f pattern frequency f The ratio f f is A.. 3 B.. 3 C. 3. D Water waves at the surface of a pond pass a floating log of length L. The log is at rest relative to the bank. The diagram shows wave crests at one instant. L The number of crests passing the log per unit time is N. The speed of the water waves relative to the log at rest is A. L (N ). 7 B. L (N ). 6 C. L (N). 7 D. L (N). 6

3 5. A sound emitting source moves along a straight line with speed v relative to an observer at rest. Observer v The speed of sound relative to the medium is c. The observer measures the speed of sound emitted by the source as A. c. B. c + v. C. c v. D. v c. 6. Standing waves in an open pipe come about as a result of A. reflection and superposition. B. reflection and diffraction. C. superposition and diffraction. D. reflection and refraction. 7. A standing wave is established on a string between two fixed points. T A B D U C At the instant shown, point T is moving downwards. Which arrow gives the direction of movement of point U at this instant? A. A B. B C. C D. D 3

4 8. Graph P shows how the displacement at one point in a wave varies with time. Graph Q shows how the displacement in the same wave varies with distance along the wave at one particular time. Graph P displacement 0 0 t t time Graph Q displacement 0 0 x x x 3 distance Which one of the following expressions gives the speed of the wave? A. B. C. D. 9. Waves x t x t ( x x ) ( t t ) ( x x ) 3 ( t t ) (a) Distinguish, in terms of the propagation of energy, the difference between a transverse travelling wave and a longitudinal travelling wave (3) 4

5 (b) The diagram below shows an aluminium rod AB of length.50 m hanging horizontally from two strings. string string hammer A.50 m B aluminium rod End A of the rod is hit gently with a hammer. As a result, a wave pulse travels down the rod and is reflected from end B. The hammer remains in contact with the rod until the pulse reflected from end B reaches A. This pulse causes the hammer to rebound from the end of the rod. (i) Suggest, giving a reason, whether the wave pulse is longitudinal or transverse. () (ii) The hammer is in contact with end A of the rod for s. Calculate the speed of the pulse in the rod. () 5

6 (iii) As a result of the rod being hit with the hammer, a sound is heard. Suggest how this sound arises. (3) (Total 0 marks) 0. This question is about waves. (a) With reference to the direction of energy transfer through a medium, distinguish between a transverse wave and a longitudinal wave (3) 6

7 (b) A wave is travelling along the surface of some shallow water in the x-direction. The graph shows the variation with time t of the displacement d of a particle of water. d / mm t / s Use the graph to determine for the wave (i) the frequency,.... () (ii) the amplitude... 7

8 (c) The speed of the wave in (b) is 5 cm s. Deduce that the wavelength of this wave is.0 cm () (d) The graph in (b) shows the displacement of a particle at the position x = 0. On the axes below, draw a graph to show the variation with distance x along the water surface of the displacement d of the water surface at time t = s. d / mm x/cm (3) 8

9 (e) The wave encounters a shelf that divides the water into two separate depths. The water to the right of the shelf is deeper than that to the left of the shelf. direction of travel of wave wave fronts 30 shelf shallow water deep water The angle between the wavefronts in the shallow water and the shelf is 30. The speed of the wave in the shallow water is 5 cm s and in the deeper water is 0 cm s. For the wave in the deeper water, determine the angle between the normal to the wavefronts and the shelf (3) (Total 4 marks) 9

10 . This question is about some properties of waves associated with the principle of superposition. Stationary (standing) waves and resonance (a) State two ways in which a standing wave differs from a continuous wave... () (b) State the principle of superposition as applied to waves () (c) A stretched string is fixed at one end. The other end is vibrated continuously to produce a wave along the string. The wave is reflected at the fixed end and as a result a standing wave is set up in the string. The diagram below shows the displacement of the string at time t = 0. The dotted line shows the equilibrium position of the string. free end fixed end 0

11 (i) The period of oscillation of the string is T. On the diagrams below, draw sketches T T of the displacement of the string at time t = and at time t =. 4 T t = 4 T t = () (ii) Use your sketches in (i) to explain why the wave in the string appears to be stationary. ()

12 (d) Stationary waves are often associated with the phenomenon of resonance. (i) Describe what is meant by resonance. () (ii) On 9 September 985 an earthquake occurred in Mexico City. Many buildings that were about 80 m tall collapsed whereas buildings that were taller or shorter than this remained undamaged. Use the data below to suggest a reason for this. period oscillation of an 80 m tall building =.0 s speed of earthquake waves = m s average wavelength of the waves =. 0 4 m (3) (Total 3 marks)