AQA A Level Physics Paper 1 2020 MS PAPER 1, Exams of Physics

Download AQA A Level Physics Paper 1 2020 MS PAPER 1 and more Exams Physics in PDF only on Docsity! AQA} A-LEVEL PHYSICS 7408/1 Paper 1 Mark scheme June 2020 Version: 1.0 Final *206A74081/MS* Physics - Mark scheme instructions to examiners 1. General The mark scheme for each question shows: the marks available for each part of the question the total marks available for the question the typical answer or answers which are expected extra information to help the Examiner make his or her judgement and help to delineate what is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in which a mark or marks may be awarded. The extra information is aligned to the appropriate answer in the left-hand part of the mark scheme and should only be applied to that item in the mark scheme. At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a calculation; or the answer may be on the diagram or at a different place on the script. In general the right-hand side of the mark scheme is there to provide those extra details which confuse the main part of the mark scheme yet may be helpful in ensuring that marking is straightforward and consistent. 2. Emboldening 2.1 Ina list of acceptable answers where more than one mark is available ‘any two from’ is used, with the number of marks emboldened. Each of the following bullet points is a potential mark. 2.2 A bold and is used to indicate that both parts of the answer are required to award the mark. 2.3 Alternative answers acceptable for a mark are indicated by the use of or. Different terms in the mark scheme are shown by a/ ; eg allow smooth / free movement. 3. Marking points 3.1 Marking of lists This applies to questions requiring a set number of responses, but for which candidates have provided extra responses. The general principle to be followed in such a situation is that ‘right + wrong = wrong’. Each error / contradiction negates each correct response. So, if the number of errors / contradictions equals or exceeds the number of marks available for the question, no marks can be awarded. However, responses considered to be neutral (often prefaced by ‘Ignore’ in the mark 4 MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - scheme) are not penalised. 32 Marking procedure for calculations Full marks can usually be given for a correct numerical answer without working shown unless the question states ‘Show your working’. However, if a correct numerical answer can be evaluated from incorrect physics then working will be required. The mark scheme will indicate both this and the credit (if any) that can be allowed for the incorrect approach. However, if the answer is incorrect, mark(s) can usually be gained by correct substitution / working and this is shown in the ‘extra information’ column or by each stage of a longer calculation. A calculation must be followed through to answer in decimal form. An answer in surd form is never acceptable for the final (evaluation) mark in a calculation and will therefore generally be denied one mark. 33 __ Interpretation of ‘it’ Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject. 34 Errors carried forward, consequential marking and arithmetic errors Allowances for errors carried forward are likely to be restricted to calculation questions and should be shown by the abbreviation ECF or conseq in the marking scheme. An arithmetic error should be penalised for one mark only unless otherwise amplified in the marking scheme. Arithmetic errors may arise from a slip in a calculation or from an incorrect transfer of a numerical value from data given in a question. 35 Phonetic spelling The phonetic spelling of correct scientific terminology should be credited (eg fizix) unless there is a possible confusion (eg defraction/refraction) with another technical term. 36 Brackets (.....) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. 37 Ignore / Insufficient / Do not allow ‘Ignore’ or ‘insufficient’ is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. ‘Do not allow’ means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded. 3s Significant figure penalties Answers to questions in the practical sections (7407/2 - Section A and 7408/3A) should display an appropriate number of significant figures. For non-practical sections, an A-level paper may contain up to 2 marks (1 mark for AS) that are contingent on the candidate 6 MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - You may well need to read back through the answer as you apply the mark scheme to clarify points and assure yourself that the level and the mark are appropriate. Indicative content in the mark scheme is provided as a guide for examiners. It is not intended to be exhaustive and you must credit other valid points. Students do not have to cover all of the points mentioned in the indicative content to reach the highest level of the mark scheme. An answer which contains nothing of relevance to the question must be awarded no marks. MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - Question Answers Additional comments/Guidelines Mark detwits 01.1 Award each mark independently 2 2x Lepton number not conserved therefore not Aon possible[] Lepton numbers for particles correct Any incorrect quantum number g equation (for Q, B or S) loses MP2. Eg 0 = 1-1-1 (for lepton number) Alternative for MP2 OR 0 = 0-1 +0 (for muon lepton ect en reference to missing muon neutrino in number) order to balance/conserve (muon) lepton number. 01.2 up anti- Either order 1 AOla up AND Credit down anti-down]] symbols But do not condone any use of capital letter 01.3 Identification of quarks in either neutral kaon Alternative: 2 AO1 correct, ie kaon d § Kaon has strangeness +10] a OR anti-kaon ds Anti-kaon has strangeness -1 AO1 Identification of quarks in other kaon correct, with statement that they are not the same. J] and is therefore not the same.[] Allow max 1 if * quark configurations wrong way round. ¢ value of strangeness is wrong way round e¢ statement that strangeness is different without reference to MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - value. e strangeness and quarks given but one of them is incorrect. MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - pd).0 Condone ‘go round the circuit’ for ‘reach anode’. MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - 02.4 MP1 is for range of KEQ] Example statements: AO1b MP2 for what happens when V is negative in MP1: photoelectrons are released terms of kinetic energy or potential energy or with a range of KE. work done on/by electron[] MP2: (When V negative) photoelectrons MP3 is for link to fewer photoelectrons having lose KE/gain (E)PE crossing to anode. necessary KE. [] MP3: (As Vis increasingly negative) fewer of the photoelectrons (released per second) have sufficient (initial) KE to cross to anode (so current decreases). 02.5 Award each mark independently If no mention of maximum KE do not AO3.1a Stopping potential related to maximum kinetic energy of photoelectrons/ K Emax = eV.{] (Max) KE = energy of photon - work function/ @. OR (max) KE increases as (work function is lower and) radiation same{] (max) KE increases, so stopping potential increases. O award MP1. Alternative Reference to Einstein equation in the form: hf=o+ev. 0 rearranged to V O So lower work function,( with hf and e constant,) gives higher Vs. 9] _ eo ~~ e Total 12 MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - Question Answers Additional comments/Guidelines Mark details 03.1 Understanding that for coherence sources must 2 AOL have same frequency/wavelength AND constant phase difference. [J a AO1 And that this achieved by both speakers being b connected to same signal (generator). 0 03.2 The sound waves from the two speakers Do not accept ‘interfere’ or 3 2x superpose (at a point) 9] ‘superimpose’ for ‘superpose’ AO2.1 g Accept for MP1 waves adding 1x together/combine at a point (e.g. point AOQO2.1 A) for ‘superpose’. c Do not accept diagram. Award MP3 for formation of At A (and B) the two waves are in phase/ have zero | minimum/destructive interference due phase difference (and a maximum is produced)[] to (odd number of) half wavelength Moving away from A introduces a path path difference/ m/ 180° phase difference/phase difference/waves are out of difference/ antiphase. phase (and amplitude decreases) [J (Moving on towards B the waves move back in phase) 03.3 Clear evidence of use of Pythagoras [] If ws/D used to give 0.13 (m) reward with 3 AO2.1h Correct calculation of either length PB or QB 4] PB = (2.25? + (0.95 - 0.3/2)’) “ = 2.39 m QB = (2.25? + (0.95 + 0.3/2)) “= 2.50m (Path difference =) QB - PB either numerically or algebraically] 1 mark MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - Question Answers Additional comments/Guidelines Mark details 04.1 Evidence of distance travelled = area under graph Full marks can be credited for use of 3 AO3.1 = 1755 + 1440 + 1620 = 48157] a Average speed = total distance/time taken = suvat. Allow ecf for distance in MP2 AO2.1f 4815/240 2 Only award MP3 for incorrect speed if AO3.1 = 20.1 ms"{] (at least 3sf) attempt made to calculate distance a Which is less than (speed) limit, (and therefore the | Correctly / answer is No). [] e.g. area under graph OR a.e. in distance or speed Alternative for MP2 and MP3 Alternative for MP1 and Calculation of distance travelled at speed limit = MP2: Total area = 80.25 m 5280 m{] s? min] Time = 4 min Which is greater than distance travelled (so no). 9 Average = 20.1ms"JJ 04.2 Award MP2 if 1.6 s (to give 50 m) or 1.8 AO3.1 Using reaction time of 2.0s] s (to give 56 m) or 17 s (to give 53 m) a or average of two distances used Use of distance = speed x time = AOla 62 m. 62 m (would be appropriate). o Allow 60 m. MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - 04.3 If no other mark given, allow 1 4 AOQ2.1b Use of F = ma to calculate acceleration. mark for my = 1200 x 31 (= 37200) a= 6800/1200] = 5.7 ms* evidence of use of suvat to calculate s or t, J] Alternative for MP1 and MP2 to give t= 5.5sfj mv—mu s=85m.]] t= F Allow ce for a. Allow ce for either incorrect s or t. Question Answers Additional comments/Guidelines Mark detwits 04.4 (It is assumed that) the car in front would take the 1 AO3 same time/travel the same distance as the car behind when braking/ only difference is reaction time of the driver of car behind. Or Car in front cannot stop instantaneously (so car behind will have time/distance to bring car to rest).or words to that effect Alternative: suggestion that total stopping distance is too large (drivers would ignore it/inefficient use of motorway) MARK SCHEME - A-LEVEL PHYSICS - 7408/1 - Question Answers Additional comments/Guidelines Mark detwits 04.5 Correct use of cos (5) [] 4 AO3.1la E.g. mg = Ncos (5) Correct use of sin (5) [] E.g. | May see cos (85) for sin (5) Nsin (5) (= mv2/r) So Alternative for MP1 and 2) nl MP2: Evidence of mg tan (5) mv’"/r seen| fourth mark is for answer and And v = (rg tan(5)) % suggesting this as the speed limit. Gives v = (200 x 9.81 x tan (5)) % = 13 Max 3 if mg = N used So speed limit = 13 ms"q Total 14