Preliminary Course Physics – Module 8.2 The World Communicates

Summative Test

Student Name: ______________________ Date: ____/____/____

IMPORTANT FORMULAE AND CONSTANTS v = f.I1/d2 n2/n1 = v1/v2 = sin i/sin r Speed of sound in a vacuum, c = 3 x 108 m/s

Part A. Multiple Choice Questions 1-20. (Circle the letter of the correct answer.) 1. The difference between a transverse wave and longitudinal wave is the: A) wavelength of the wave. B) medium through which the wave travels. C) speed of the wave. D) direction of vibration relative to the wave motion. 2. Two corks, X and Y, are floating on the water.

Which of the following best describes what happens to the two corks as the wave advances? A) X moves up and Y moves down. B) X moves down and Y moves up. C) X and Y move forward. D) X and Y move up and then forward. 3. A wave generater dipping into water in a ripple tank has a period of l/6 s. The resulting wave has a wavelength of 0.02 m. What is the speed of the wave? A) 0.02 m/s B) 0.12 m/s C) 3 m/s D) 6 m/s 4. When green light travels from water to air, what are the changes, if any, to its velocity, frequency and wavelength? Velocity Frequency Wavelength A) Unchanged Increased Decreased B) Unchanged Decreased Increased C) Decreased Unchanged Decreased D) Increased Unchanged Increased

Preliminary Course Physics – Module 8.2 The World Communicates 5. An echo-sounder on a ship produced a pulse of sound, the echo of which was received by an echo-sounder after 2 seconds.

What is the depth of the sea? (The speed of sound in water is 1500 m/s.) A) 750m B) 1600m C) 1500m D) 4000m 6. The diagrams represent sound waves displayed on an oscilloscope. Assuming the controls of the oscilloscope remain the same for each sound, which diagram represents the quietest sound with the highest frequency? A) B) C) D)

7. The diagram below shows a ray of light travelling across a water-air boundary.

What are the correct names of rays X and Y and angle Z? X Y Z A) Incident Refracted Incidence B) Emergent Incident Critical C) Refracted Incident Incidence D) Incident Refracted Critical

Preliminary Course Physics – Module 8.2 The World Communicates 8. A ray of light is incident on a piece of glass block as shown in the figure below.

Which of the following expressions should be used to calculate the refractive index of the glass block? A) sin 40o/sin 30o B) sin 50o/sin 30o C) sin 30o/sin 50o D) sin 30o/sin 40o

9. The diagram below shows a plane mirror placed at a distance of 400 cm in front of a man. If the doctor's test card is fixed at 70 cm behind the eyes of the man, what is the distance of the image from the man?

A) 470 cm B) 800 cm C) 870 cm D) 940 cm

10. The bottom surface of a glass block is silvered to act as a mirror. Which of the following diagrams could represent the path of a light ray which enters this block through the top surface? A) B) C) D)

11. Which of the following statement(s) is/are true about a transverse wave? I It carries energy. II It has compressions and rarefactions. III Its speed depends on the medium. IV The vibration of its particles is parallel to the direction in which the wave travels. V A water ‘ripple’ is an example. A) I, II and III only B) I, III and V only C) II, III and IV only D) II,III and V only

Preliminary Course Physics – Module 8.2 The World Communicates 12. The diagram below shows an antenna emitting an electromagnetic wave.

In what way did the electrons in the antenna produce the electromagnetic wave? A) by remaining stationary. B) by moving at constant speed upward only. C) by moving at constant speed downward only. D) by accelerating alternatively upward and downward. 13. The diagram below shows two sources of waves, A and B, vibrating in phase in the same uniform medium and producing circular wavefronts.

Which wave phenomenon occurs at point P? A) destructive interference B) constructive interference C) attenuation D) inversion 14. Two guitar strings are tuned to the same pitch. If one string is plucked, the other string nearby vibrates with the same frequency. This phenomenon is called: A) attenuation B) inversion C) propagation D) resonance

Preliminary Course Physics – Module 8.2 The World Communicates 15. The diagram below shows two waves approaching each other in the same uniform medium.

Which diagram best represents the appearance of the medium, after the waves have passed through each other? A) B) C) D) 16. The diagram below represents two pulses approaching each other.

Which diagram best represents the resultant pulse at the instant the pulses are passing through each other? A) B) C) D)

17. Which of the following contains only devices that use data in digital format? A) Computers, CD players and home telephones B) DVD players, cathode ray tube televisions and mobile phones C) Home telephones, mobile phones and GPS devices D) CD players, DVD players and MP3 players 18. Radio waves diffract around buildings more than light waves do because, compared to light waves, radio waves: A) move faster B) move slower C) have a higher frequency D) have a longer wavelength

Preliminary Course Physics – Module 8.2 The World Communicates 19. The diagram below shows a ray of light passing from air into glass at an angle of incidence of 0°.

Which statement best describes the speed and direction of the light ray as it passes into the glass? A) Only speed changes. B) Only direction changes. C) Both speed and direction change. D) Neither speed nor direction changes. 20. Which wave characteristic is the same for all types of electromagnetic radiation traveling in a vacuum? A) speed B) period C) wavelength D) frequency Part B. Free Response. Answer in the spaces provided. 21. In a ripple tank experiment, a train of water waves are produced by a straight vibrator of frequency I0 Hz. The train of waves goes from a region A to another region B of different depths through a straight boundary PQ as shown in the diagram below (not drawn to scale). The distance between two successive crests of the waves in region A is 0.03 m while that of the waves in region B is 0.02 m.

a) What is the speed of the waves in region A? (1 mark) __________________________________________________________________________________________ b) What is the speed of the waves in region B? (1 mark) __________________________________________________________________________________________

Preliminary Course Physics – Module 8.2 The World Communicates Q21 continued c) Which region, A or B, is deeper? Explain. (2 marks) __________________________________________________________________________________________ d) If the wavefront in A makes an angle of 30o with PQ, what is the angle which the wavefront in B makes with PQ? (2 marks) __________________________________________________________________________________________ 22. A wave is caused to travel along a spring by moving end X as shown in the diagram below.

a) Mark on the diagram, the wavelength of this wave with the letter “”. Hence determine the wavelength of this wave from your diagram. (2 marks) __________________________________________________________________________________________ b) State whether this wave is a transverse or longitudinal wave. Justify your choice. (2 marks) __________________________________________________________________________________________ __________________________________________________________________________________________ 23. Outline the energy transformations that occur in ONE of the following devices: (3 marks)

mobile telephone fax/modem radio television

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Preliminary Course Physics – Module 8.2 The World Communicates 24. The diagram below shows the main components of the electromagnetic spectrum in order of increasing frequency.

a) What are the names of the missing components marked A, B and C? (3 marks) A = __________________________ B = ___________________________ C = _________________________ b) Which components of the electromagnetic spectrum are filtered out by the Earth’s atmosphere? (3 marks) _________________________________________________________________________________________ c) Identify how any TWO components of the EM spectrum can be detected. (2 marks) __________________________________________________________________________________________ 25. The diagrams below represent different wave properties.

#1 #2 #3 For EACH diagram: a) Identify the wave property shown. b) Give a clear account of how the new directions of the wavefronts can be predicted after they have undergone the changes shown. (9 marks) __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________

Preliminary Course Physics – Module 8.2 The World Communicates 26. The figure below shows a ship placed at different positions above the seabed to determine its depth profile. The ultrasound wave information obtained from the different positions is also given.

Transmitted Pulses and Their Echoes at Positions a and b

Transmitted Pulses and Their Echoes at Positions c and d

Transmitted Pulses and Their Echoes at Positions e and f

Preliminary Course Physics – Module 8.2 The World Communicates Q26. continued a) Given that the speed of the ultrasound in seawater is 1500 m.s-1, how long does it take to detect the echo if the depth being measures is 300 m? (1 mark) __________________________________________________________________________________________ b) Based on the information of the echoes, calculate the corresponding depth of each position of the seabed. Write your final answers in the table shown below, but show your working below the table. (3 marks) Position Above Seabed a b c d e f Calculated depth (m) __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ c) Draw in the space below the depth profile of the seabed. Indicate clearly the depth of the seabed at each position. (3 marks)

27. Describe the structure of an optical fibre and explain how optical fibres carry light. (4 marks)

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Preliminary Course Physics – Module 8.2 The World Communicates 28. A student performs an experiment to demonstrate the refraction of light by a rectangular glass block. The diagram shows, to scale, the outline of the glass block and the paths of the incident and emergent rays, that the student draws on a piece of paper.

a) Describe the apparatus needed and also a method by which the paths of the incident and emergent rays may be drawn on a piece of paper. (4 marks) __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ b) Take measurements from the diagram above to find the refractive index of the glass block. Show clearly your working, state the equation that you use and give your answer to an appropriate number of significant figures. (3 marks) __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________

Preliminary Course Physics – Module 8.2 The World Communicates c) The student repeats the experiment with the incident ray at different angles. The values obtained for the angles x and y shown in the diagram are given in the table below. X (o) 0 10 20 30 40 50 60 70 80 Y (o) 0 7 13 20 26 31 36 39 42 Plot a graph of sin x against sin y on the grid below. Your axes should end at y = 50o and x = 90o. Draw the line of best fit through your points. (4 marks)

(d) (i) Use your graph to estimate the critical angle for glass and explain how you obtained your result. (2 marks) __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________

Preliminary Course Physics – Module 8.2 The World Communicates (ii) Explain why it is impossible to obtain a value of y = 50o in this experiment. (1 mark) __________________________________________________________________________________________ __________________________________________________________________________________________ e) The glass block used in the experiment is replaced by one having a larger refractive index. The experiment is repeated and a second graph is plotted. State one similarity and one difference between this second graph and the graph obtained in part c). (2 marks) __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________