AQA A LEVEL PHYSICS MARKING SCHEME PAPER 1 2020| UPDATE 2022 100% CORRECT

Candidate signat A-level ure PHYSICS Paper 1 Monday 18 May 2020 Afternoon Time allowed: 2 hours Materials For this paper you must have: • a pencil and a ruler • a scientific calculator • a Data and Formulae Booklet. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Do all rough work in this book. Cross through any work you do not want to be marked. • Show all your working. Information • The marks for questions are shown in brackets. • The maximum mark for this paper is 85. • You are expected to use a scientific calculator where appropriate. • A Data and Formulae Booklet is provided as a loose insert. *JUN20740 101* IB/M/Jun20/E11 7408/1 Section A Answer all questions in this section. Do not write outside the box . 1 Determine whether the following reaction is a possible decay for the neutral pion π0. π0 → e− + μ+ + ve [2 marks] . 2 State the two possible quark configurations of a π0. [1 mark] 1 2 . 3 A student suggests that the kaon K0 and the anti-kaon K0 are the same particle. Discuss whether this suggestion is correct. [2 marks] . 4 The nucleus is held together by a force. It was predicted that a particle exists that is responsible for this force. The particle itself must experience this force. The particle would have a rest energy between that of an electron and half that of a nucleon. Discuss whether a kaon, a muon and a pion each have the properties of the predicted particle. Do not write outside the box Information about these three particles is in the Data and Formulae Booklet. [4 marks] Turn over for the next question Turn over ► Do not write outside the Figure 1 shows an arrangement used to investigate the photoelectric effect. Figure 1 A current is measured on the microammeter only when electromagnetic radiation with a frequency greater than a certain value is incident on the photoemissive surface. . Explain why the frequency of the electromagnetic radiation must be greater than a certain value. Do not write outside the box [2 marks] The apparatus in Figure 1 is used with a monochromatic light source of constant intensity. Measurements are made to investigate how the current I in the microammeter varies with positive and negative values of the potential difference V of the variable voltage supply. Figure 2 shows how the results of the investigation can be used to find the stopping potential. Figure 2 0 2 Do not write outside the box . Determine the number of photoelectrons per second leaving the photoemissive surface when the current is a maximum. [2 marks] number of photoelectrons per second = Question 2 continues on the next page Turn over ► Do not write outside the box . 3 Explain why I reaches a constant value for positive Do not write outside the box values of V. [2 marks] . 4 Explain why I decreases as the value of V becomes more negative. [3 marks] . 5 The investigation is repeated with a different photoemissive surface that has a smaller value of the work function. The source of electromagnetic radiation is unchanged. Do not write outside the box Discuss the effect that this change in surface has on the value of the stopping potential. [3 marks] Turn over for the next question *07* Downloaded by: 692Nurse | Turn over ► 3 A student investigates the interference of sound waves using two loudspeakers, P and Q, connected to a signal generator (oscillator). Each loudspeaker acts as a point source of sound. Figure 3 shows the arrangement. Figure 3 Point O is the midpoint between P and Q. . 1 Explain why the two loudspeakers are coherent sources of sound waves. [2 marks] Do not write outside the box *0 * Downloaded by: 692Nurse | . 2 The student faces the two loudspeakers at point A. Point A is at equal Do not write outside the box distances from P and Q. He then moves to point B, at right angles to the line OA, still facing the two loudspeakers. As his head moves from A to B the amplitude of the sound wave he hears decreases and then increases. The amplitude starts to decrease again as he moves beyond B. Explain why the variation in amplitude occurs as he moves from A to B. [3 marks] Question 3 continues on the next page Turn over ► Do not write outside the . 3 The student records the following data: separation of the two loudspeakers = 0.30 m distance OA = 2.25 m distance from A to B = 0.95 m Show that the path difference for the sound waves from the two loudspeakers to point B is about 0.1 m. [3 marks] Do not write outside the box . 4 The frequency of the sound wave is 2960 Hz. Calculate the speed of sound from the student’s data. [1 mark] speed of sound = m s−1 0 3 . 5 The student moves his head to point C as shown in Figure 4. The emitted frequency of the sound from the loudspeakers is then gradually decreased. Figure 4 Discuss the effect that this decrease in frequency has on the amplitude of the sound wave heard by the student. Do not write outside the box [3 marks] Turn over ► There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box A pa0ir cameras is used on a motorway to help determine the average speed of Do not write outside the box vehicles travelling between the two cameras. Figure 5 shows the speed–time graph for a car moving between the two cameras. Figure 5 . 1 The speed limit for the motorway between the two cameras is 22 m s−1. Determine whether the average speed of the car exceeded this speed limit. [3 marks] Question 4 continues on the next page Turn over ► Do not write outside the . 2 Markings called chevrons are used on motorways. The chevron separation is designed to give a driver time to respond to any change in speed of the car in front. The driver is advised to keep a minimum distance d behind the car in front, as shown in Figure 6. Figure 6 Government research suggests that the typical time for a driver to respond is between 1.6 s and 2.0 s. Do not write outside the box Suggest a value for d where the speed limit is 31 m s−1. [2 marks] d = m . 3 The chevron separation is based on the response time, not on the time taken for a car to stop. The brakes of a car are applied when its speed is 31 m s−1 and the car comes to rest. The total mass of the car is 1200 kg. The average braking force acting on the car is 6.8 kN. Do not write outside the box Calculate the time taken for the braking force to stop the car and the distance travelled by the car in this time. [4 marks] time = s distance = m . 4 Suggest why the chevron separation on motorways does not take into account the distance travelled as a car comes to rest after the brakes are applied. [1 mark] Question 4 continues on the next page Turn over ► Do not write outside the 0 4 . At bends on motorways the road is sloped so that a car is less likely to slide out of its lane when travelling at a high speed. Figure 7 shows a car of mass 1200 kg travelling around a curve of radius 200 m. The motorway is sloped at an angle of 5.0°. Figure 8 shows the weight W and reaction force N acting on the car. The advisory speed for the bend is chosen so that the friction force down the slope is zero. Do not write outside the box Figure 7 *21* Downloaded by: 692Nurse | Suggest an appropriate advisory speed for this section of the motorway. [4 marks] Do not write outside the box advisory speed = m s−1 14 Turn over for the next question *17* Downloaded by: 692Nurse | Turn over ► Figu0r shows some of the apparatus used in a demonstration of electrical power Do not write outside the box transmission using a dc power supply. Figure 9 A power supply of emf 12 V and negligible internal resistance is connected to three identical 12 V, 1.5 W lamps in parallel. . 1 Show that the resistance of one of the lamps when it is operating at 12 V is about 100 Ω. [1 mark] . 2 Initially the power supply is connected to the lamps using two short copper wires of negligible resistance. Calculate the current in the power supply. [2 marks] current = A *1 * Downloaded by: 692Nurse | 0 5 . The two short copper wires are replaced with two long constantan wires. Show that the resistance of each length of constantan wire is about 50 Ω. Do not write outside the box length of each constantan wire diameter of constantan wires resistivity of constantan = 2.8 m = 0.19 mm = 4.9 × 10−7 Ω m [3 marks] 0 5 . The demonstration is intended to show that the lamps are significantly dimmer when connected using the long constantan wires than when using the short copper wires. Discuss whether the demonstration achieves this. Support your answer with suitable calculations. [4 marks] Question 5 continues on the next page Turn over ► Do not write outside the box Section B Each of Questions 06 to 30 is followed by four responses, A, B, C and D. For each question select the best response. Do not write outside the box Only one answer per question is allowed. For each question, completely fill in the circle alongside the appropriate answer. CORRECT METHOD WRONG METHODS If you want to change your answer you must cross out your original answer as shown. If you wish to return to an answer previously crossed out, ring the answer you now wish to select as shown. You may do your working in the blank space around each question but this will not be marked. Do not use additional sheets for this working. Mechanical power [1 mark] A is a vector quantity. B is measured in J. C has base units of kg m2 s−3. D can be calculated from force × distance moved. 0 7 Water waves of wavelength λ and wave speed v are related by v = k where k is a constant. What is a possible SI unit for k? A m s−2 B m s−1 [1 mark] 3 C m2 s−1 1 D m2 s−1 Turn over ► Do not write outside the box 88 What quantity is measured in kW h? [1 mark] Do not write outside the box A charge B current C energy D power 1 2 An electron collides with an isolated atom and raises an atomic electron to a higher energy level. Which statement is correct? [1 mark] A The colliding electron is captured by the nucleus of the atom. B A photon is emitted when the electron rises to the higher energy level. C An electron is emitted when the excited electron returns to the ground state. D The colliding electron transfers energy to the atomic electron. Turn over for the next question Turn over ► Do not write outside the box Which graph shows the variation of momentum p with wavelength λ of a photon? [1 mark] Do not write outside the box A B C D A B C D A m1o hromatic light wave travels from glass into air. Which row shows what happens to the wavelength, speed and photon energy? [1 mark] Wavelength Speed Photon energy A increases increases increases B does not change decreases does not change C does not change decreases increases D increases increases does not change A wave travels across the surface of water. The diagram shows how the displacement of water particles at the surface varies with distance. Do not write outside the box Which row correctly describes both w and z? [1 mark] w z A amplitude wavelength B half-amplitude period C half-amplitude wavelength D amplitude period Do not write outside the Turn over ► 1 6 The diagram shows the cross-section of a progressive transverse wave travelling at 24 cm s−1 on water. The amplitude of the wave is 2.0 cm and the frequency is 4.0 Hz. Do not write outside the box Which statement is correct? A The phase difference between particles at P and S is