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CLASSIFIED 3

IGCSE

Mr. Hussam Samir

MR. HUSSAM SAMIR CLASSIFIED 3 IGCSE

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1. A police car with its siren sounding is stationary in heavy traffic. A pedestrian notices that, although the loudness of the sound produced does not change, the pitch varies. Which line in the table describes the amplitude and the frequency of the sound?

2. A starting pistol is fired 640 m away from a spectator.

The spectator hears the sound of the starting pistol two seconds after seeing the flash from the gun. What is the speed of sound in air? A) 160 m / s B) 320 m / s C) 640 m / s D) 1280 m / s

3. Fig. 7.1 is a drawing of a student’s attempt to show the diffraction pattern of water waves that have passed through a narrow gap in a barrier.


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(a) State two things that are wrong with the wave pattern shown to the right of the barrier. 1. ..................................................................................................................................... 2. ................................................................................................................................. (b) In the space below, sketch the wave pattern when the gap in the barrier is made five times wider. (c) The waves approaching the barrier have a wavelength of 1.2 cm and a frequency of 8.0 Hz. Calculate the speed of the water waves. speed = ..................................

4. A girl stands in front of a rock face. The girl claps her hands once. The speed of sound in air is 330m/ s. How long is it before she hears the echo?

5. Fig. 6.1 shows the diffraction of waves by a narrow gap. P is a wavefront that has passed through the gap. (a) On Fig. 6.1, draw three more wavefronts to the right of the gap.

(b) The waves travel towards the gap at a speed of 3 x108m/s and have a frequency of 5 x 10

14 Hz.

Calculate the wavelength of these waves. wavelength = ................................


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6. Fig. 7.1 is drawn to full scale. The focal length of the lens is 5.0 cm.

(a) On Fig. 7.1, mark each principal focus of the lens with a dot and the letter F. (b) On Fig. 7.1, draw two rays from the tip of the object O that appear to pass through the tip of the image.

(c) On Fig. 7.1, draw the image and label it with the letter I. (d) Explain why the base of the image lies on the axis. ......................................................................................................................................... ................................................................................................................................... (e) State a practical use of a convex lens when used as shown in Fig. 7.1. ...................................................................................................................................

7. (a) Fig. 6.1 shows the results of an experiment to find the critical angle for light in a semicircular glass block. The ray of light PO hits the glass at O at an angle of incidence of 0°. Q is the centre of the straight side of the block. (i) Measure the critical angle of the glass from Fig. 6.1. critical angle = .................... (ii) Explain what is meant by the critical angle of the light in the glass.

(b) Fig. 6.2 shows another ray passing through the same block.

The speed of the light between W and Q is 3.0 x108m/s. The speed of

the light between Q and Y is

2.0 ×108m/s.

(i) State the speed of the light between Y and Z. speed = ......................................


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(ii) Write down an expression, in terms of the speeds of the light, that may be used to find the refractive index of the glass. Determine the value of the refractive index. refractive index = ........................ (iii) Explain why there is no change of direction of ray QY as it passes out of the glass. (iv) What happens to the wavelength of the light as it passes out of the glass? 8. Two sound waves P and Q are displayed on an oscilloscope with the same time-base and Y-plate settings for each.

Which statement correctly describes the pitch and the loudness of the two sounds? A) P has a higher pitch and is louder than Q. B) P has a higher pitch and is quieter than Q. C) P has a lower pitch and is louder than Q. D) P has a lower pitch and is quieter than Q.

9. The image of a clock face as seen in a plane mirror is shown. What is the time on the clock? A) 1.25 B) 1.35 C) 10.25 D) 10.35


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10. What is the unit of wavelength? A hertz B metre C metre per second D second

11. Which row correctly describes light waves and radio waves?

12. The image formed by a plane mirror is upright.

What are the other characteristics of the image?


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13. A girl stands at a distance from a large building. She claps her hands and a short time later hears an echo. Why is an echo produced when the sound waves hit the building? A The sound waves are absorbed. B The sound waves are diffracted. C The sound waves are reflected. D The sound waves are refracted.

14. The diagrams represent the waves produced by four sources of sound. The scales are the same for all the diagrams. Which sound has the highest frequency?

15. Sound travels by wave motion. Which property of waves causes echoes? A diffraction B dispersion C reflection D refraction


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16. A student draws three rays of light from point P through a converging lens. Each point labelled F is a principal focus of the lens.

Which of the rays are drawn correctly? A ray Y only B ray Z only C ray X and ray Y D ray X and ray Z

17. (a) Fig. 8.1 shows a section of an optical fibre. It consists of a fibre of denser transparent material, coated with a layer of a less dense transparent material.

One ray within the fibre has been started for you on Fig. 8.1. (i) State and explain what happens to the ray already drawn, after it reaches the boundary between the materials. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[2]


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18. (a) What is meant by the focal length of a converging lens? ................................................................................................................................................... ...............................................................................................................................................[1] (b) An object is placed in front of a converging lens. A real image is formed, as shown in Fig. 7.1. The converging lens is not shown.

(i) Explain what is meant by a real image. .......................................................................................................................................[1] (ii) Rays of light from point A on the object form point B on the image. On Fig. 6.1, draw 1. a ray to find the position of the converging lens, showing the lens as a vertical straight line in this position, 2. a ray to find the position of a principal focus of the lens, marking this position F, 3. a third possible ray from A to B. [3] (iii) The distance between the object and the lens is increased. State any changes which take place in 1. the distance of the image from the lens, ........................................................................................................................................... 2. the size of the image. .......................................................................................................................................[2]

19. The diagram shows a ray of light travelling from X. Angle P is less than the critical angle. In which direction does the ray continue?


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20. (a) Fig. 6.1 shows the position of layers of air, at one moment, as a sound wave of constant frequency passes through the air. Compressions are labelled C. Rarefactions are labelled R.

(i) State how Fig. 6.1 would change if 1. the sound had a higher frequency, ................................................................................................................................[1] 2. the sound were louder. .................................................................................................................................... .................................................................................................................................... ................................................................................................................................[2] (ii) On Fig. 6.1, draw a line marked with arrows at each end to show the wavelength of the sound. [1] (b) In an experiment to measure the speed of sound in steel, a steel pipe of length 200 m is struck at one end with a hammer. A microphone at the other end of the pipe is connected to an accurate timer. The timer records a delay of 0.544 s between the arrival of the sound transmitted by the steel pipe and the sound transmitted by the air in the pipe. The speed of sound in air is 343 m / s. Calculate the speed of sound in steel. speed of sound in steel = .......................................................... [3]

21. The diagrams show the wave shapes of two different sounds. The scales are the same in each diagram.

How does sound 2 compare with sound 1? A Sound 2 is louder than sound 1. B Sound 2 is quieter than sound 1. C Sound 2 has a higher pitch than sound 1. D Sound 2 has a lower pitch than sound 1.


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22. (a) Fig. 7.1 shows a ray of monochromatic red light, in air, incident on a glass block at an angle of incidence of 50°.

(i) State what is meant by monochromatic light. .......................................................................................................................................[1] (ii) For this red ray the refractive index of the glass is 1.52. Calculate the angle of refraction for the ray. angle of refraction = ...........................................................[2] (iii) Without measuring angles, use a ruler to draw the approximate path of the ray in the glass block and emerging from the block. [2] (b) The red ray in Fig. 7.1 is replaced by a ray of monochromatic violet light. For this violet ray the refractive index of the glass is 1.54. The speed of light in air is 3.00 × 108 m / s. (i) Calculate the speed of the violet light in the glass block. speed = ...........................................................[2] 23. A student listens to a machine that makes sounds of different frequencies. He can only hear one of the sounds. Which frequency of sound is the student able to hear? A 2 Hz B 10 Hz C 2 kHz D 30 kHz


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24. A navigation buoy floating on the sea oscillates up and down as a wave passes.

In exactly two minutes, six complete wavelengths pass the buoy. What is the frequency of the waves? A 0.050 Hz B 0.33 Hz C 3.0 Hz D 20 Hz 25. The diagram shows a ray of light incident on the edge of a piece of glass. The angle i is bigger than the critical angle. Which arrow correctly shows the direction of the ray after it leaves the edge of the glass?

26. A police car siren emits two different sounds P and Q. These are produced alternately. The diagram represents the sounds emitted. Which sound is the louder and which has the lower pitch?


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27. In an optics lesson, a Physics student traces the paths of three rays of light near the boundary between medium A and air. The student uses a protractor to measure the various angles. Fig. 8.1 illustrates the three measurements.

(a) State which is the optically denser medium, A or air, and how you can tell this. .......................................................................................................................................... .................................................................................................................................... [1] (b) State in which medium the light travels the faster, and how you know this. .......................................................................................................................................... .................................................................................................................................... [1] (c) State the critical angle of medium A. ................................................... [1]


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(d) State the full name for what is happening to ray 3. ................................................... [1] (e) The refractive index of medium A is 1.49. Calculate the value of the angle of refraction of ray 1, showing all your working. angle of refraction = ................................................ [2]

(f) The speed of light in air is 3.0 108 m / s. Calculate the speed of light in medium A, showing all your working. speed of light = ................................................ [2]

28. Fig. 8.1 shows a thin converging lens. The two principal foci are shown.

A vertical object, 2 cm tall, is to be positioned to the left of the lens, with one end on the principal axis. On Fig. 8.1, (a) draw the object in a position which will produce a virtual image, labelling the object with the letter O, [1] (b) draw two rays showing how the virtual image is formed, [2]

(c) draw in the image, labelling it with the letter I. [1]

29. Which range of frequencies typically can be heard by a 10 year-old child? A 20 Hz – 2000 Hz B 20 Hz – 20 000 Hz C 200 Hz – 2000 Hz D 200 Hz – 20 000 Hz


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30. Astronaut 1 uses a hammer to mend a satellite in space. Astronaut 2 is nearby. There is no air in space.

Compared with the sound heard if they were working on Earth, what does astronaut 2 hear? A a louder sound B a quieter sound C a sound of the same loudness D no sound at all

31. Fig. 6.1 shows a rectangular glass block ABCD.

(a) The ray FE is partly reflected and partly refracted at E. (i) On Fig. 6.1, draw in the approximate path of the refracted ray, within and beyond the block. Label the ray refracted ray. [1] (ii) On Fig. 6.1, draw in the path of the reflected ray. Label the ray reflected ray. [1] (b) A second ray, almost parallel to AE, strikes the block at E and is partly refracted at an angle of refraction of 43°. (i) State an approximate value for the angle of incidence at E. ................................................. [1] (ii) State an approximate value for the critical angle for the light in the glass block. ................................................. [1] (iii) Calculate an approximate value for the refractive index of the glass of the block. refractive index = ................................................ [2]


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(c) The speed of the light along ray FE is 3.0 x 108 m/s. Calculate the speed of the refracted light in the glass block. speed = ................................................ [2]

32. Two students are asked to determine the speed of sound in air on the school playing fields. (a) List the apparatus they need. .......................................................................................................................................... .......................................................................................................................................... .................................................................................................................................... [1] (b) List the readings that the students need to take. .......................................................................................................................................... .......................................................................................................................................... .................................................................................................................................... [1] (c) State how the speed of sound is calculated from the readings. .................................................................................................................................... [1] (d) State one precaution that could be taken to improve the accuracy of the value obtained. .......................................................................................................................................... .................................................................................................................................... [1] (e) The table gives some speeds.

Place a tick in the table to show the speed which is closest to (i) the speed of sound in air, (ii) the speed of sound in water.

33. Which line gives an example of a longitudinal wave and describes its vibrations?


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34. A student shines a narrow beam of white light into a prism as shown in the diagram. He sees a spectrum of colours emerging from the prism.

Which three colours does he see at X, at Y and at Z?

35. A girl stands at a distance from a large building. She claps her hands and a short time later hears an echo. Why is an echo produced when the sound waves hit the building? A The sound waves are absorbed. B The sound waves are diffracted. C The sound waves are reflected. D The sound waves are refracted.

36. The IGCSE class is investigating the formation of images by a lens. Fig. 4.1 shows the apparatus that is being used.

(a) A student places the screen at a distance d = 0.800 m from the illuminated object. She adjusts the position of the lens until a clearly focused magnified image is formed on the screen. She measures the distance x between the centre of the lens and the screen. Without moving the illuminated object or the screen, she moves the lens towards the screen until a second clearly focused (but diminished) image is formed on the screen. She measures the distance y between the centre of the lens and the screen. She repeats the experiment with the distance d increased to 0.900 m. The readings are shown in the table.


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(i) For each set of readings calculate the focal length f of the lens using the equation

Enter the values in the table.

(ii) Calculate the average value of the focal length f. average value of the focal length f = ................................................ [4] (b) Suggest two precautions that can be taken in this experiment in order to obtain an accurate result. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... .................................................................................................................................... [2] (c) The illuminated object is triangular in shape, as shown in Fig. 4.2.

In the space below, sketch the appearance of one of the images on the screen.

37. When the horn on a ship is sounded, the passengers hear an echo from a cliff after 4.0 s. If the speed of sound is 340 m / s, how far away is the cliff? A 170 m B 340 m C 680 m D 1360 m


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38. Fig. 6.1 shows a ray of light OPQ passing through a semi-circular glass block.

(a) Explain why there is no change in the direction of the ray at P. .......................................................................................................................................... ..................................................................................................................................... [1] (b) State the changes, if any, that occur to the speed, wavelength and frequency of the light as it enters the glass block. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) At Q some of the light in ray OPQ is reflected and some is refracted. On Fig. 6.1, draw in the approximate positions of the reflected ray and the refracted ray. Label these rays. [2] (d) The refractive index for light passing from glass to air is 0.67. Calculate the angle of refraction of the ray that is refracted at Q into air. angle = ………………. [3]

39. Fig. 7.1 shows the parts of the electromagnetic spectrum.

(a) Name one type of radiation that has (i) a higher frequency than ultra-violet,


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.............................................................................................................................. [1] (ii) a longer wavelength than visible light. .............................................................................................................................. [1]

(b) Some rays emitted from a radioactive source have a speed in air of 3.0 x 108m/s and a wavelength of 1.0 x 10–12m.

Calculate the frequency of the -rays. frequency = ………………. [2] (c) State the approximate speed of infra-red waves in air. ..................................................................................................................................... [1]

40. An IGCSE student is determining the focal length of a lens. Fig. 4.1 shows the experimental set-up. The student positions the illuminated object and the lens and then moves the screen away from the lens until a sharply focused image of the object is formed on the screen.

(a) Using your rule, measure on Fig. 4.1 the distance u, in cm, from the centre of the lens to the illuminated object and the distance v from the centre of the lens to the screen. u = ........................................... v =............................................ [2] (b) (i) Fig. 4.1 is drawn one fifth actual size. Calculate the actual distance x from the illuminated object to the centre of the lens and the actual distance y from the centre of the lens to the screen. Record these values in Table 4.1. The first pair of readings obtained by the student has already been entered in the table.

(ii) Calculate for both pairs of readings the focal length f of the lens using the equation

Record the values of f in Table 4.1.


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(c) Calculate the average value of the focal length. average value for the focal length = ....................................... [2] (d) State two precautions you would take in the laboratory in order to obtain reliable measurements. 1. ...................................................................................................................................... 2. ................................................................................................................................. [2]

41. Fig. 7.1 shows the cone of a loudspeaker that is producing sound waves in air. At any given moment, a series of compressions and rarefactions exist along the line XY.

(a) On Fig. 7.1, use the letter C to mark three compressions and the letter R to mark three rarefactions along XY. [1] (b) Explain what is meant by (i) a compression, ................................................................................................................................... ................................................................................................................................... (ii) a rarefaction. ................................................................................................................................... ................................................................................................................................... [2] (c) A sound wave is a longitudinal wave. With reference to the sound wave travelling along XY in Fig. 7.1, explain what is meant by a longitudinal wave. .......................................................................................................................................... ...................................................................................................................................... [2] (d) There is a large vertical wall 50 m in front of the loudspeaker. The wall reflects the sound waves. The speed of sound in air is 340 m/s. Calculate the time taken for the sound waves to travel from X to the wall and to return to X. time = …………………[2]

42. Which of these waves is longitudinal? A light waves B sound waves C water waves D X-ray waves


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43. Waves move from deep water to shallow water where they are slower. Which diagram shows what happens to the waves?

44. Which type of radiation lies between visible light and microwaves in the electromagnetic spectrum? A infra-red B radio waves C ultra-violet D X-rays 45. The critical angle for a glass / air boundary is C. Which diagram shows the correct path of the light ray?

46. What is the approximate range of audible frequencies for most humans? A 10 Hz to 10 000 Hz B 20 Hz to 20 000 Hz C 10 kHz to 10 000 kHz D 20 kHz to 20 000 kHz 47. A plane mirror is on a wall. Which is a correct description of the image formed by the mirror? A the right way up and smaller than the object B the right way up and the same size as the object C upside down and smaller than the object D upside down and the same size as the object


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48. A student is determining a quantity called the refractive index of the material of a transparent block. Fig. 4.1 shows the ray-tracing sheet that the student is producing. ABCD is the outline of the transparent block, drawn on the ray-tracing sheet.

(a) (i) Draw the normal NN' to side AB, extended to cross side DC, so that the normal is 2.0 cm from A. Label the point F where NN' crosses AB. Label the point G where NN' crosses DC. (ii) Draw the line EF at an angle of 30° to the normal and to the left of the normal NN'. E is a point outside the block and above AB on the ray-tracing sheet. [3] (b) Read the following passage, taken from the student’s notebook and then answer the questions that follow.


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(i) Draw a line joining the positions of P3 and P4. Continue the line until it meets CD. Label this point H. (ii) Measure and record the length a of the line GH. a = ...................................................... (iii) Draw the line HF. (iv) Measure and record the length b of the line HF. b = .................................................. [3] (c) Extend the straight line EF through the outline of the block to a point J. The point J must be at least 5 cm from the block. The line EJ crosses the line CD. Label this point K. (i) Measure and record the length c of the line GK. c = ...................................................... (ii) Measure and record the length d of the line FK. d = ...................................................... (iii) Calculate the refractive index n of the material of the block using the equation

n = ..................................................

49. An IGCSE student is determining the focal length of a lens by two different methods. The set-up for Method 1 is shown in Fig. 4.1. [3]

The student moves the lens and the mirror slowly towards the object screen until a sharply focused image is obtained on the object screen as shown in Fig. 4.2.


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(a) On Fig. 4.1, use your rule to measure the distance f between the lens and the object screen. This is the focal length of the lens. f = ................................................ [2] (b) For Method 2, the student takes measurements of the diameter d and maximum thickness t of the lens. Use your rule to take measurements on Fig. 4.3.

(i) Determine an average value for the diameter d of the lens. Record your readings in the space below. d = ...................................................... (ii) Measure the maximum thickness t of the lens. t = ...................................................... (iii) Draw a diagram to show how, in the laboratory you would use two rectangular blocks of wood and a metre rule to measure the thickness of the lens as accurately as possible. (iv) Theory shows that, for a perfectly formed lens, the focal length is given by the Formula

where k = 4.16. Calculate the focal length f of the lens using this formula.

f = ......................................................

50. What is the approximate value of the highest frequency that can be heard by a young person? A 20 Hz B 200 Hz C 2000 Hz D 20 000 Hz


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55. The diagram shows water waves passing through a gap in a harbour wall. The waves curve round the wall and reach a small boat in the harbour.

What is the name of this curving effect, and how can the gap be changed so that the waves are less likely to reach the boat?

56. The drawing shows a wave. Which labelled distance is the wavelength?

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