*B16* Pre-Leaving Certi cate Examination, 2017 Triailscrúdú na hardteistiméireachta, 2017 PHYSICS ORDINARY LEVEL TIME: 3 HOURS Answer three questions from Section A and ve questions from Section B. Relevant data are listed in the Formulae and Tables booklet, which is available from the Superintendent. Page 1 of 11
SECTION A (120 marks) Answer three questions from this section. Each question carries 40 marks. 1. A student carried out an experiment to measure g, the acceleration due to gravity. (i) Draw a labelled diagram of the apparatus used. (12) (ii) State the measurements taken during the experiment. (6) (iii) Describe how the student took these measurements. (9) (iv) How was a value for g calculated from the measurements? (9) (v) Give one precaution taken to get an accurate result. (4) 2. A student carried out an experiment to measure the speci c latent heat of fusion of ice. The following is an extract from his report. In my experiment, I got ice which was at 0 C and I added it to warm water in a calorimeter. I waited for all the ice to melt before taking more measurements. I used my measurements to calculate the speci c latent heat of fusion of ice. (i) Draw a labelled diagram of the apparatus used in the experiment. (10) (ii) What measurements would the student have taken for this experiment? (6) (iii) How did the student prepare the ice for the experiment? (6) (iv) How did the student know the ice was at 0 C? (6) (v) Why did the student use warm water in the experiment? (6) (vi) Why was the experiment repeated? (6) Page 2 of 11
3. A student carried out an experiment to verify Snell s law of refraction by measuring the angle of incidence i and the angle of refraction r for a ray of light entering a glass block. The student repeated this procedure two more times. The data recorded by the student is shown in the table. (i) Draw a labelled diagram of the apparatus used in the experiment. (12) (ii) Describe how the student found the position of the refracted ray. (9) (iii) How did the student measure the angle of refraction? (4) (iv) Copy this table and complete it in your answer book. (9) angle of incidence i angle of refraction r sin i sin r sin i / sin r 30 19 0.50 0.33 55 33 70 40 (v) Use the data to verify Snell s law of refraction. (6) 4. In an experiment to investigate how current varied with voltage across a solution, a student collected the following data. V (V) 0 1 2 3 4 5 6 7 8 I (A) 0 0.3 0.6 0.8 1.2 1.3 1.6 1.8 2.1 (i) Draw a suitable diagram for this experiment and label the components. (12) (ii) How was the potential difference measured in the experiment? (6) (iii) Using the data in the table, draw a graph on graph paper to show the variation of current with potential difference. (10) (iv) Calculate the slope of your graph. (6) (v) Use this value to determine the resistance of the solution. (6) Page 3 of 11
SECTION B (280 marks) Answer ve questions from this section. Each question carries 56 marks. 5. Answer any eight of the following parts (a), (b), (c), etc. (a) State the principle of conservation of momentum. (b) A car accelerates from 10 m s 1 to 30 m s 1 in 5 seconds. What is its acceleration? (v = u + at). (c) Which one of the following is the unit of power? joule kelvin kilogram watt (d) Name one method by which heat can be transferred. (e) Name a pair of complementary colours. (f) Infrared radiation is part of the electromagnetic spectrum. Name two other radiations that are part of the electromagnetic spectrum. (g) Name the electrical component represented in the diagram. (h) List two safety devices that are used in household electric circuits. (i) What is the photoelectric effect? (j) Name a material used as shielding in a nuclear reactor. (8 7) Page 4 of 11
6. De ne pressure. (6) Describe an experiment to show that the atmosphere exerts pressure. (9) The earth is covered with a layer of air called the atmosphere. What holds this layer of air close to the earth? (6) The type of weather we get depends on the atmospheric pressure. Describe the kind of weather we get when the atmospheric pressure is high. (6) A man and a woman are walking together on soft ground. The man has a mass of 80 kg and is wearing at shoes that have an area of 0.05 m 2 in contact with the ground. The woman has a smaller mass of 60 kg and is wearing high heels that have an area of 0.02 m 2 in contact with the ground. (i) Find the weight of the man and the woman. (9) (ii) Calculate the pressure exerted by the woman on the ground. (6) (iii) Calculate the pressure exerted by the man on the ground. (3) (iv) Why is the woman more likely than the man to sink in the soft ground? (5) (v) Calculate the pressure exerted by the man if he carried the woman across the soft ground. (6) g = 9.8 ms -2 Page 5 of 11
7. The diagram shows a waveform. X Y (i) What is the name given to the distance (a) X, (b) Y? (6) (ii) How many wavelengths are shown in the diagram? (6) (iii) What is meant by the frequency of a wave? (6) (iv) Explain the term natural frequency? (6) (v) If the natural frequency of a vibrating string is 250 Hz, calculate the wavelength of the sound produced. (9) (vi) State the wave property on which (a) the loudness and (b) the pitch of a musical note depends. (9) Resonance can occur between objects of the same natural frequency. (vii) Describe a laboratory experiment to demonstrate resonance. (14) (c = f, speed of sound in air = 340 m s 1 ) Page 6 of 11
8. (i) State Ohm s Law. (9) The graphs show how current (I) varies with potential difference (V) for (a) a metal, (b) a lament bulb. I I (a) a metal V Which conductor obeys Ohm s law? Explain your answer. (12) Another type of conductor is a semiconductor. What is a semiconductor? (7) The circuit diagram shows a resistor and a thermistor connected in series with a 6 V battery. At a certain temperature the resistance of the thermistor is 450. V (b) a lament bulb 6 V 50 450 (ii) What is the total resistance of the circuit? (7) (iii) What is the current in the circuit? (7) (iv) What is the potential difference across the 50 resistor? (7) (v) What would happen to the resistance of the circuit if the temperature were increased? (7) Page 7 of 11
9. A magnetic eld exists in the vicinity of a magnet. What is a magnetic eld? (6) Draw a sketch of the magnetic eld around a bar magnet. (9) Describe an experiment to show that a current carrying conductor in a magnetic eld experiences a force. List two factors that affect the size of the force on the conductor. (18) A coil of wire is connected to a sensitive galvanometer as shown in the diagram. S N What is observed when the magnet is moved towards the coil? (6) Explain why this occurs. (6) Describe what happens when the speed of the magnet is increased. (6) Give one application of this effect. (5) 10. Nuclear energy can be produced by nuclear fusion and nuclear ssion. Nuclear fusion releases the energy that causes all stars, including our Sun, to exist for billions of years. Nuclear ssion releases the energy that is produced in nuclear reactors in many countries throughout the world. neutron ssion product neutron neutron target nucleus ssion product neutron (i) What is the difference between nuclear fusion and nuclear ssion? (6) Nuclear ssion occurs in a nuclear reactor. (ii) What is the role of neutrons in nuclear ssion? (6) (iii) Name a fuel used in a nuclear reactor. (6) (iv) In a nuclear reactor, how can the ssion be controlled or stopped? (6) (v) How is the energy produced in a nuclear reactor used to generate electricity? (6) (vi) Give one advantage and one disadvantage of a nuclear reactor as a source of energy. (6) (vii) What is the role of (a) the control rods and (b) the moderator in a nuclear reactor? (8) Na 25 is a radioactive isotope of sodium. It has a half- life of 1 minute. (viii) Explain the term half-life. (6) (ix) What frac tion of a sample of Na 25 remains after 3 minutes? (6) Page 8 of 11
11. Read this passage and answer the questions below. Li-Fi has just been tested in the real world, and it s 100 times faster than Wi-Fi Expect to hear a whole lot more about Li-Fi - a wireless technology that transmits high-speed data using visible light. Li-Fi and Wi-Fi are quite similar as both transmit data electromagnetically. However, Wi-Fi uses radio waves while Li-Fi runs on visible light. With scientists achieving speeds of 224 Gbits per second in the lab using Li- Fi earlier this year, the potential for this technology to change everything about the way we use the Internet is huge. And now, scientists have taken Li-Fi out of the lab for the rst time, trialling it in of ces and industrial environments in Estonia, reporting that they can achieve data transmission at 1 GB per second - that s 100 times faster than current average Wi-Fi speeds. Li-Fi was invented by Harald Haas from the University of Edinburgh, Scotland back in 2011, when he demonstrated for the rst time that by ickering the light from a single LED, he could transmit far more data than a cellular tower. Think back to that lab-based record of 224 gigabits per second - that s 18 movies of 1.5 GB each being downloaded every single second. The technology uses visible light of around 500 terahertz (THz). It works basically like an incredibly advanced form of Morse code - just like switching a torch on and off according to a certain pattern can relay a secret message, icking an LED on and off at extreme speeds can be used to write and transmit things in binary code. And while you might be worried about how all that ickering in an of ce environment would drive you crazy, don t worry - we re talking LEDs that can be switched on and off at speeds imperceptible to the naked eye. The bene ts of Li-Fi over Wi-Fi, other than potentially much faster speeds, is that because light cannot pass through walls, it makes it a whole lot more secure. (Adapted from physicsworld.com) (a) (b) (c) (d) (e) (f) (g) (h) What is Li-Fi? What is the difference between Li-Fi and Wi-Fi? In Estonia, they could achieve data transmission at 1 GB per second. What does G represent in Scienti c Notation? Li-Fi was demonstrated by ickering the light from an LED to transmit data. What is an LED? Name a material used as a semiconductor. Using Li-Fi, 18 movies could be downloaded every single second. How many movies could be downloaded in one hour? Visible light has a frequency, f of around 500 x 10 12 Hz. If visible light has a velocity of 3 x 10 8 m s -1, what is its wavelength,? (c = f ) State one advantage and one disadvantage of Li-Fi compared to Wi-Fi. (8 7) Page 9 of 11
12. Answer any two of the following parts (a), (b), (c), (d). (a) The pressure exerted on any object underwater varies with depth. (i) State Boyle s law. (9) (ii) How does Boyle s law explain why a bubble gets bigger as it rises towards the surface of a lake? (9) (iii) A sh starts at a depth of 20 m in water and rises to 1 m below the surface. What is the change in pressure on the sh as it makes this rise? (10) (density of water = 1000 kg m 3 ; acceleration due to gravity, g = 9.8 m s 2 ) (b) Loudness, pitch and quality are characteristics of a musical note. Name the physical property of a sound wave on which each characteristic depends. (12) A bat detector allows us to hear the sounds emitted by bats. The detector is needed as humans cannot hear the sounds as they are outside our frequency limits of audibility. (i) What is meant by the frequency limits of audibility? (6) (ii) What name is given to a sound whose frequency is greater than our upper frequency limit of audibility? (4) (iii) A bat emitted a sound wave and detected its re ection from a wall 0.02 s later. Calculate the distance of the bat from the wall. (6) (speed of sound in air = 340 m s 1 ) Page 10 of 11
(c) In an experiment to demonstrate the photoelectric effect, a piece of zinc is placed on a gold leaf electroscope, as shown. The zinc is given a negative charge causing the gold leaf to de ect. Explain why the gold leaf de ects when the zinc is given a negative charge. (9) Ultraviolet radiation is then shone on the charged zinc and the gold leaf falls. Explain why. (9) What is observed when the experiment is repeated using infrared radiation? (6) Give one application of the photoelectric effect. (4) (d) What is electromagnetic induction? (10) The diagram shows a transformer. (i) Name the parts labelled A and B. (6) (ii) The input voltage is 230 V. Part B has 4600 turns and part C input B output C has 120 turns. Calculate the output voltage. (6) A Vi V0 N N p s (iii) Name a device that uses a transformer. (6) Page 11 of 11
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