Physics Topic 6: Waves (MASTER Booklet)

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for this anomalous result? Tick one box. Student B Timing less than five echoes. Page 3 of 38 (e) (f) (g) Timing more than five echoes. Calculate the mean value of the time for 5 echoes. Ignore the anomalous result. The distance between student A and the building is 75 metres. Calculate the distance the sound travels in going from student A to the building and back again five times. mean time = Calculate the speed of sound. Use your answers to Questions (e) and (f) and the equation: distance travelled speed = 1. 2. distance = Page 4 of 38 time speed of sound = (h) The value for the speed of sound obtained by the students is not very accurate. Suggest two changes to the method used by the students that would improve the accuracy. S m m/s (1) (1) (1) (2) Q2. (a) Figure 1 shows what happens to rays of light incident on three different surfaces. Figure 1 (b) XXXX A Which one of the diagrams shows diffuse reflection? Tick one box. B C B 8% 100% Figure 2 shows what happens to the energy transferred by a ray of light when the ray of light hits a glass block. Figure 2 #f C /90% Calculate the percentage of the energy absorbed by the glass block. (2) (Total 10 marks) Percentage of energy absorbed = Page 5 of 38 % (c) Viewing an object through a colour filter may make the object look a different colour. Complete the sentences. Choose the answers from the box. (1) (1) (d) 1. 2. This is the method used. 3. absorbs red 4. (e) black reflects Cyclists often wear clothing that reflects a lot of light. Figure 3 shows a student investigating which colours are best at reflecting light. Figure 3 A red object viewed through a blue filter will look This is because the red object only blue filter only blue transmits A white surface is viewed through a green filter. What colour will the surface look? blue light. 0 00 red light and the Small squares of different coloured material were stuck onto a piece of black paper at one end of a darkened laboratory. Page 6 of 38 The student switched on a torch and walked slowly towards the coloured squares. The student stopped walking as soon as he could clearly see a coloured square. The student measured the distance between the torch and the coloured square. Give a reason why it was important the student did the investigation in a darkened laboratory. (3) (1) (1) (f) The table shows the student's results. Give a reason why it was important the area of each coloured square was the same. (g) (h) Distance from the torch to 4.0 Figure 4 shows a bar chart with only three of the student's results. Figure 4 3.0 the square 2.0 in metres 1.0- Colour of square 0 Blue Brown Green Orange Red Blue Distance from the torch to the square in metres Brown 2.3 2.1 3.2 3.4 2.6 Green Colour of square Complete the bar chart to show all of the results. Which colour clothing would be best for a cyclist to wear? Use the data from the table. Page 7 of 38 (1) (3) (i) Q3. (a) (b) Tick one box. Blue Give a reason for your answer. Brown accurate The student did the investigation again to obtain a second set of results. The second set of results showed the same pattern as the first set. Complete the sentence. Choose the answer from the box. Green Gamma rays Sound Ultraviolet The measurements taken by the student were X-rays precise Orange Which one of the following is not an electromagnetic wave? Tick one box. repeatable Page 8 of 38 What type of electromagnetic wave do our eyes detect? Red reproducible (2) (1) (Total 14 marks) (1) (1) (c) What is a practical use for infrared waves? Tick one box. Cooking food Energy efficient lamps Medical imaging Satellite communications Scientists have detected radio waves emitted from a distant galaxy. Some of the radio waves from the distant galaxy have a frequency of 1 200 000 000 hertz. (d) Which is the same as 1 200 000 000 hertz? Tick one box. 1.2 gigahertz 1.2 kilohertz 1.2 megahertz 1.2 millihertz ☐ Page 9 of 38 (1) (1) (e) (f) (g) Q4. (a) Radio waves travel through space at 300 000 kilometres per second (km/s). How is 300 000 km/s converted to metres per second (m/s)? Tick one box. 300 000 1000 = 300 m/s 300 000 × 1000 = 300 000 000 m/s 300 000 + 1000 = 301 000 m/s 300 000 1000 299 000 m/s Write the equation which links frequency, wavelength and wave speed. Calculate the wavelength of the radio waves emitted from the distant galaxy. Give your answer in metres. Ultrasound is sound above the maximum frequency that humans can hear. Tick (✓) one box. 20 Hz wavelength = Page 10 of 38 m (1) (1) (3) (Total 9 marks) (b) (c) (d) 2000 Hz 20 000 Hz The image shows a submerged submarine. half Submarine Distance to sea floor Sea floor The submarine sends a pulse of ultrasound to the sea floor. The pulse takes 0.25 seconds to travel from the submarine to the sea floor. The speed of sound in water is 1600 m/s. Calculate the distance from the submarine to the sea floor. The ultrasound is reflected from the sea floor back to the submarine. Use the correct answer from the box to complete the sentence. Pulse number the same as Not to scale The total distance the ultrasound pulse travelled is sea floor. Distance = Time for pulse to return in seconds The submarine moves through the sea and every few seconds sends a pulse of ultrasound to check the distance to the sea floor. Page 11 of 38 twice The table shows the time taken for five ultrasound pulses to travel from the submarine to the sea floor and back to the submarine. the distance to the (1) (2) (1) 1 2 3 4 5 Describe how the distance from the submarine to the sea floor changed over these five pulses. (a) (i) Q5. Figure 1 shows a ray of light travelling through a semicircular glass block. The angle of incidence is labelled i. (ii) Ray box 0.50 0.45 0.38 0.40 0.48 Glass block Air Figure 1 The angle of incidence i equals the critical angle for the glass. Complete Figure 1 to show what happens to the ray of light at the glass-to-air boundary. The critical angle for the glass is 41°. Calculate the refractive index of the glass. (2) (Total 6 marks) Page 12 of 38 (1) (b) Q6. Refractive index = Figure 2 shows what happens to a ray of light as it meets the boundary between air and water. Air Water Figure 2 35% The refractive index of the water is 1.3. Angle of refraction = Calculate the angle of refraction r. degrees Not to scale Page 13 of 38 Small water waves are created in a ripple tank by a wooden bar. The wooden bar vibrates up and down hitting the surface of the water. The figure below shows a cross-section of the ripple tank and water. mandmeng (3) (Total 6 marks) Ripple tank (2) Not to scale (a) (b) Which letter shows the amplitude of a water wave? Tick one box. J K L The speed of the wooden bar is changed so that the bar hits the water fewer times each second. What happens to the frequency of the waves produced? Tick one box. Increases Does not change Decreases (c) Describe how the wavelength of the water waves in a ripple tank can be measured accurately. (d) The speed of a wave is calculated using the following equation. Page 14 of 38 (1) (1) (2) Q7. (a) wave speed = frequency x wavelength The water waves in a ripple tank have a wavelength of 1.2 cm and a frequency of 18.5 Hz. (b) How does the speed of these water waves compare to the typical speed of a person walking? Different parts of the electromagnetic spectrum are useful for different methods of communication. The diagram shows a transmitter emitting two electromagnetic waves, L and M. (i) (ii) Transmitter M The Earth D Wave M is reflected by the ionosphere. Satellite lonosphere Wave L is used to send a signal to a satellite. Which part of the electromagnetic spectrum does wave L belong to? Page 15 of 38 Receiver (4) (Total 8 marks) What name is given to the process that occurs as wave L passes into the ionosphere? (1) (1) (c) (i) On the diagram above, draw the path of wave M until it reaches the receiver. (b) (ii) On the daigram above, draw a line to show the normal where wave M meets the ionosphere. Label the line N. Give two properties of all electromagnetic waves. 1. 2. Q8. X-rays and ultrasound can both be used for scanning internal organs. (a) Ultrasound is used to scan unborn babies but X-rays are not used to scan unborn babies. Explain why. The behaviour of ultrasound waves when they meet a boundary between two different materials is used to produce an image. Describe how. Page 16 of 38 (2) (2) (Total 7 marks) (1) (3) (2) (c) Figure 1 shows two pulses from a scan of an unborn baby. The emitted pulse is labelled A. The returning pulse picked up by the receiver is labelled B. Figure 1 A B ILL. 10 20 30 40 50 60 70 80 90 100 Time in seconds x 10-6 Pulse intensity The closest distance between the unborn baby and the mother's skin is 4.0 cm. Use information from Figure 1 to calculate the average speed of the pulse. (d) Figure 2 shows an X-ray of an arm with a broken bone. Figure 2 Ⓒemmy-images/iStock Average speed = Page 17 of 38 m/s (3) (i) (ii) (b) Describe how X-rays are able to produce an image of bones. Complete the following sentence. X-rays are able to produce detailed images because their wavelength is very Q9. Bats use the reflection of high pitched sound waves to determine the position of objects. The image below shows a bat and an insect flying in front of the bat. Insect (a) What determines the pitch of a sound wave? Tick (✓) one box. amplitude frequency speed Tick (✓) Sound waves emitted by bat State the name given to reflected sound waves. Page 18 of 38 (3) (1) (Total 12 marks) (1) (c) The bat emits a sound wave with a frequency of 25.0 kHz and a wavelength of 0.0136 metres. Calculate the speed of this sound wave. (d) Sound waves are longitudinal. Describe a longitudinal sound wave. Q10. Figure 1 shows an X-ray of an arm with a broken bone. Figure 1 Ⓒ emmy-images/iStock (a) Complete the following sentence. X-rays are part of the spectrum. Speed = Page 19 of 38 m/s (1) (2) (2) (Total 6 marks) (1) (b) Figure 2 shows how the intensity of the X-rays changes as they pass through soft tissue and reach a detector. Intensity of X-rays in arbitrary units (ii) 10 9 8 7- 6- 5- 4- 3- 2- 1 0 Figure 2 2 Thickness of soft tissue in cm (i) Use Figure 2 to determine the intensity of X-rays reaching the detector for a 3 cm thickness of soft tissue. Intensity of X-rays = 4 5 Page 20 of 38 arbitrary units Describe how the thickness of soft tissue affects the intensity of the X-rays. (1) (2) (c) (d) (e) (iii) The data in Figure 2 are shown as a line graph and not as a bar chart. Choose the reason why. Tick (✓) one box. Both variables are categoric Both variables are continuous One variable is continuous and one is categoric What happens to X-rays when they enter a bone? How are images formed electronically in a modern X-ray machine? Tick (✓) one box. With a charge-coupled device (CCD) (i) With an oscilloscope With photographic film Radiographers who take X-ray photographs may be exposed to X-rays. X-rays can increase the risk of the radiographer getting cancer. Why can X-rays increase the risk of getting cancer? Tick (✓) one box. X-rays travel at the speed of light Page 21 of 38 (1) (1) (1) X-rays can travel through a vacuum (a) X-rays are ionising (ii) What should the radiographer do to reduce the risk from X-rays? Q11. The data given in the table below was obtained from an investigation into the refraction of light at an air to glass boundary. Angle of incidence 20° 30° 40° 50° Angle of refraction 13° 19° 25° 30° (1) (Total 9 marks) Describe an investigation a student could complete in order to obtain similar data to that given in the table above. Your answer should consider any cause of inaccuracy in the data. A labelled diagram may be drawn as part of your answer. Page 22 of 38 (1) (6) (b) State the reason why light is refracted as it crosses from air into glass. Q12. The figure below shows an incomplete electromagnetic spectrum. A microwaves Tick one box. infrared radio visible light B X-ray C (a) What name is given to the group of waves at the position labelled A in the figure above? ultraviolet D Page 23 of 38 gamma (1) (Total 7 marks) (1) (b) (c) Electromagnetic waves have many practical uses. Draw one line from each type of electromagnetic wave to its use. Electromagnetic wave Gamma rays Microwaves Ultraviolet Complete the sentence. Use an answer from the box. black body ionising Use For fibre optic communications For communicating with a satellite To see security markings Page 24 of 38 To sterilise surgical instruments nuclear X-rays can be dangerous to people because X-rays are radiation. (3) (1) (Total 5 marks) Q13. A student investigated how the magnification produced by a convex lens varies with the distance (d) between the object and the lens. The student used the apparatus shown in Figure 1. Figure 1 Object slit 1 cm tall (a) (b) Ray box Distance (d) Convex lens 25 30 40 50 60 Sharp image- The data recorded by the student is given in Table 1. Table 1 Distance between the object and the lens in cm The student measured the magnification produced by the lens by measuring the image height in centimetres. Explain why the image height in centimetres was the same as the magnification. Page 25 of 38 1 Magnification 4.0 2.0 1.0 0.7 0.5 Screen It would be difficult to obtain accurate magnification values for distances greater than 60 cm. (2) (c) Suggest one change that could be made so that accurate magnification values could be obtained for distances greater than 60 cm. (e) The graph in Figure 2 is incomplete. 4.0 3.5 3.0 2.5- Magnification 2.0 1.5- 1.0- 0.5 0.0 Figure 2 10 40 20 30 50 Distance between the object and the lens in cm Distance between the lens and the image in cm (d) How many times bigger is the image when the object is 35 cm from the lens compared to when the object is 55 cm from the lens? X Complete the graph in Figure 2 by plotting the missing data and then drawing a line of best fit. During the investigation the student also measured the distance between the lens and the image. Table 2 gives both of the distances measured and the magnification. Table 2 Distance between the lens and the object in cm Page 26 of 38 60 Magnification (1) (2) (2) 100 60 40 33 30 Consider the data in Table 2. 25 30 40 50 60 4.0 2.0 1.0 0.7 0.5 Give a second way that the student could have determined the magnification of the object. Justify your answer with a calculation. Page 27 of 38 (2) (Total 9 marks) Mark schemes Q1. (a) (b) (d) (c) the oscillation should be perpendicular to the direction of the stretched spring allow up and down (e) (f) (g) (h) Q2. (a) (b) K (c) L and M timing less than five echoes 3 (.0) 750 (m) speed = 3 speed = 250 (m/s) A 750 any two from: 2 (%) black an answer of 250 (m/s) scores 2 marks reflects time more than 5 echoes students stand further from the building have 2 or more students (independently) measuring the time taken use a stopwatch with a higher resolution is insufficient transmits allow ecf from parts (e) and (f) correct order only Page 28 of 38 1 1 1 1 1 1 2 1 2 1 1 1 1 [10] (d) (e) (f) (g) (h) (i) Q3. (c) (d) (e) green (f) without a darkened laboratory would not be able to see reflected light allow would see all squares all of the time (g) so same 'amount' of light is incident on each square a fair test is insufficient control variable is insufficient two bars drawn at the correct height (a) sound both bars correctly labelled orange allow 1 mark for 1 correct bar repeatable (b) (visible) light can be seen from the furthest away reason only scores if orange chosen allow it reflects the most light cooking food 1.2 gigahertz 300 000 × 1000 = 300 000 000 m/s wave speed = frequency x wavelength allow v = fx 300 000 000 = 1200 000 000 × A an answer of 0.25 scores 3 marks Page 29 of 38 1 1 1 2 1 1 1 1 1 1 1 1 1 1 [14] Q4. (a) (b) (c) (d) 2= 300 000 000 1 200 000 000 A = 0.25 (m) 20 000 Hz 400 (m) twice allow ecf from (e) (ii) allow 1 mark for correct substitution ie 1600 × 0.25 From pulse 1 to pulse 3 the distance (to the sea floor) decreased accept the sea got shallower provided no subsequent steps shown an answer of 200 (m) gains 1 mark 1.5 then (after pulse 3) the distance (to the sea floor) increased accept the sea got deeper or the submarine went deeper for the distance decreased Q5. (a) (i) line drawn at 90 degrees to the normal: or the submarine rose for the distance increased An answer of the distance decreased then increased gains 1 mark ignore (partial) reflection of the ray Page 30 of 38 1 1 1 2 1 1 1 1 [10] [6] (b) Q6. (a) K (b) (d) 26 Q7. (a) Decreases award both marks for an answer that rounds to 1.5 award 1 mark for correct substitution ie 1/ sin 41 or 1/0.656(059) award 3 marks for an answer that rounds to 26 award 2 marks for 0.57(3576) 1.3= sin r or r = sin-¹(0.57(3576)/1.3) (c) use a metre rule / 30 cm ruler to measure across 10 (projected) waves accept any practical number of waves number for 10 sin 35 award 1 mark for correct substitution.ie 1.3 = sin r or sin 35° shown correctly, ie 0.57(3576), or used correctly in the calculation (i) an answer of 0.44 scores 2 marks an answer of 26.9 scores 0 and then divide by 10 1.2 cm = 0.012 m 18.5 x 0.012= 0.22(2) (m/s) allow 0.22(2) with no working shown for 2 marks typical walking speed = 1.5m/s accept any value e.g. in the range 0.7 to 2.0 m/s so the water waves are slower (than a typical walking speed) this cannot score on its own microwave Page 31 of 38 2 3 1 1 1 1 1 1 1 1 [6] [8] (b) (c) (ii) (i) . • refraction . wave M continues a straight line to the ionosphere and shown reflected . accept reflection at or within the ionosphere any two from: correctly reflected wave shown as a straight line reaching the top of the receiver if more than 2 rays shown 1 mark maximum Transmitter ignore arrows (ii) normal drawn at point where their M meets the ionosphere Transmitter transverse The Earth same speed (through air) WATER The Earth Satellite accept speed of light or 3 x 108 m/s Page 32 of 38 lonosphere Receiver Satellite lonosphere Receiver can be reflected can be refracted can be diffracted can be absorbed transfer energy can travel through a vacuum an answer travel at the same speed though a vacuum scores 1 1 1 1 Q8. (a) (b) (c) ● 2 marks can be polarised show interference. travel in straight lines is insufficient ultrasound is not ionising allow ultrasound does not harm the (unborn) baby but X-rays are ionising so X-rays increase the health risk to the (unborn) baby 1600 (m/s) accept specific examples of health risks, eg cancer, stunted growth, impaired brain function etc X-rays are dangerous is insufficient ultrasound/waves are partially reflected (when they meet a boundary) (between two different media / substances / tissues) must be clear that not all of the wave is reflected the time taken is measured (and is used to determine distances) 800 (m/s) gains 2 marks 160 000 (m/s) gains 2 marks 0.0016 (m/s) gains 2 marks allow 2 marks for 0.04 25x10 or 0.08 50 x 10 80 000 (m/s) gains 1 mark 0.0008 (m/s) gains 1 mark allow 1 mark for 0.04 25 or 0.08 50 allow 1 mark for evidence of doubling the distance or halving the time Page 33 of 38 2 1 1 1 1 [7] (d) (i) they are absorbed by bone allow stopped for absorbed Q9. (a) (b) (c) (ii) they are transmitted by soft tissue short (the transmitted) X-rays are detected frequency X-rays are reflected negates this mark echo(es) 340 (m/s) allow pass through for transmitted allow flesh/muscle / fat accept less (optically) dense material for soft tissue accept small allow 1 mark for correct substitution ie 25 000 × 0.0136 provided no subsequent step or allow 1 mark for a correct calculation showing an incorrect value from conversion to hertz × 0.0136 an answer of 0.34 gains 1 mark (d) (a wave where the) oscillations are parallel to the direction of energy transfer both marking points may appear as labels on a diagram accept vibrations for oscillations accept in same direction as for parallel to allow direction of wave (motion) for direction of energy transfer allow 1 mark for a correct calculation showing an incorrect value from conversion to hertz × 0.0136 causing (areas of) compression and rarefaction accept correct description in terms of particles mechanical wave is insufficient needs a medium to travel through is insufficient Page 34 of 38 3 1 1 1 1 1 1 2 1 1 [12] [6] Q10. (a) (b) (c) (d) (e) Q11. (a) electromagnetic (i) (ii) (iii) accept e.m. (i) 2.2 (arbitrary units) (ii) allow an answer between 2.1 and 2.3 the thicker the tissue the lower the intensity accept more intensity is needed to pass through thicker tissue the relationship is not linear accept the line is not straight allow for 1 mark it still goes through with thicker tissue or intensity does not reach zero or at 5 cm X rays still pass through (they are) absorbed Both variables are continuous With a charge-coupled device (CCD). accept (they are) stopped X-rays are ionising stand behind a (protective) screen accept leave the room accept wear a lead apron Level 3 (5-6 marks): A detailed and coherent plan covering all the major steps is provided. The steps in the method are logically ordered. The method would lead to the production of valid results. A source of inaccuracy is provided. Level 2 (3-4 marks): The bulk of a method is described with mostly relevant detail. The method may not be in a completely logical sequence and may be missing some detail. Page 35 of 38 1 1 1 1 1 1 1 [9] (b) Q12. Level 1 (1-2 marks): Simple statements are made. The response may lack a logical structure and would not lead to the production of valid results. (b) 0 marks: No relevant content. Indicative content place a glass block on a piece of paper draw around the glass block and then remove from the paper draw a line at 90° to one side of the block (the normal) use a protractor to measure and then draw a line at an angle of 20° to the normal replace the glass block using a ray box and slit point the ray of light down the drawn line mark the ray of light emerging from the block remove the block and draw in the refracted ray measure the angle of refraction with a protractor repeat the procedure for a range of values of the angle of incidence possible source of inaccuracy the width of the light ray which makes it difficult to judge where the centre of the ray is velocity / speed of the light decreases (a) radio allow velocity / speed of the light changes Page 36 of 38 6 1 1 [7] Q13. (c) ionising (b) Gamma rays (c) Microwaves (d) Ultraviolet image height (a) magnification = object height For fibre optic communications For communicating with a satellite award 1 mark for each correct line if more than one line is drawn from any em wave then none of those lines gain credit both points plotted correctly correct line of best fit drawn To see security markings dividing by an object height of 1 cm gives the same (numerical) value To sterilise surgical instruments accept anything practical that would work eg: use a taller object use a (travelling) microscope attach a scale to the screen and use a magnifying glass 2.33 times bigger a curve passing through all points (within ½ square), judge by eye values of 1.4 and 0.6 extracted from the graph Page 37 of 38 3 1 1 1 1 1 1 [5] accept any number between 2.3 and 2.5 inclusive (e) by dividing the distance between the lens and the image by the distance between the lens and the object 1 Page 38 of 38 1 at least one correct calculation and comparison eg 100÷25 = 4 which is the same as the measured magnification 1 [9]