2822 Electrons and Photons. June Mark Scheme

Size: px

Start display at page:

Download "2822 Electrons and Photons. June Mark Scheme"

James Manning
5 years ago
Views:

1 2822 Electrons and Photons June 2003 Mark Scheme

2 Categorisation of marks The mark scheme categorises marks on the MACB scheme. B marks: These are awarded as independent marks, which do not depend on other marks. For a B-mark to be scored, the point to which it refers must be seen specifically in the candidate s answers. M marks: These are method marks upon which A-marks (accuracy marks) later depend. For an M-mark to be scored, the point to which it refers must be seen in the candidate s answers. If a candidate fails to score a particular M-mark, then none of the dependent A-marks can be scored. C marks: These are compensatory marks which can be scored if the point to which they refer are not written down by the candidates, providing subsequent working gives evidence that they must have known it. For example, if an equation carries a C-mark and the candidate does not write down the actual equation but does correct working which suggest he/she knew the equation, then the C-mark is awarded. A marks: These are accuracy or answer marks which either depend on an M-mark, or allow a C-mark to be scored.

3 The following annotations may be used when marking: X = incorrect response (errors may also be underlined) ^ = omission mark bod = benefit of the doubt (where professional judgement has been used) ecf = error carried forward (in consequential marking) con = contradiction (in cases where candidates contradict themselves in the same response) sf = error in the number of significant figures Abbreviations, annotations and conventions used in the Mark Scheme: / = alternative and acceptable answers for the same marking point ; = separates marking points NOT = answers not worthy of credit ( ) = words which are not essential to gain credit (underlining) = key words which must be used ecf = allow error carried forward in consequential marking AW = alternative wording ora = or reverse argument

4 (a) Any two from: Travel through a vacuum (NOT travel through space, but allow free-space ) Travel at the speed of light / (ms - ) (in vacuum) They consist of photons Consist of oscillating electric and magnetic fields They are transverse wave / They can be polarised They can be diffracted / reflected / refracted / interfered x2 (- for each contradictory statement) (b) v = fλ / c = fλ (Wave equation with any subject) C λ = / C λ = (m) A (c) Wavelength in the range: 0-6 to 0-2 (m) (Allow upper limit of 0 - (m) for the wavelength) [Total 6] 2 (a) Arrow (within the lemon and) towards the negative terminal (b)(i) ΔQ = IΔt (Allow other subject. Δ is not necessary) C charge = C charge = (C) (- for 0 n error and - for t = 8 days) A (ii) P = VI C P = (ECF for current from b(i)) P = A unit: W / Js - / VA [Total 7] 3 (a) 2 = / + 2 = + / = / = C = 72 (Ω) (- for each error) A XY = = 72 (Ω) (Allow 70) (Possible ECF) A (b) Any four marks from: esistance of thermistor decreases as temperature increases (ora) B2 (esistance of circuit changes with temperature scores mark) The voltmeter reading / voltage stays constant / at 4.5 (V) (AW) The ammeter reading / current increases The current is inversely proportional to the resistance of the thermistor One mark for QWC (Spelling and grammar) [Total 8]

5 4 (a) V = M V = 2.24 V 2.2 V A0 (b) V = V = 9.76 (V) 9.8 (V) (c)(i) area = π ( ) 2 / area = π /0 6 M area = (m 2 ) (m 2 ) A0 (ii) = ρl/a (Allow any subject) C = / C = (Ω) (- if (m 2 ) is not used from c(i)) A (iii) The resistance decreases by a factor of eight M because area increases by a factor of four and length decreases A ( (Ω) with correct working scores 2/2) ( (Ω) without working scores /2) (Allow /2 for esistance decreases by a factor of four because length decreases and area increases by a factor of two scores ) [Total 8] 5 A correct potential divider circuit with LD, voltmeter, (variable) resistor and cell (allow a battery) Correct symbols for LD, cell (allow battery), variable resistor and voltmeter (- for an error or omission) Any five from: (These must be stated and not from the diagram) The (variable) resistor and LD are connected in series (to the cell) The voltmeter is placed across (variable) resistor / LD 2V0 V V = / = + 2 V2 2 quoted The resistance of LD decreases as intensity of light increases (AW) Correct description of how voltage/voltmeter reading changes with light intensity The change in voltage / voltmeter reading is justified in terms of potential divider / ratio of resistance values / I = V/( + 2 ) and V = I 2 Correct description of how the (circuit) current is affected by intensity The variable resistor is used for sensitivity / determining range / calibration / (monitor) different light levels One mark for QWC (Organisation) [Total 9]

6 6 (a)(i) Into (plane of) paper (ii) Correct region to the left of the conductor (b) F = BIL (Allow any subject) C B = / ( ) B = A unit: tesla / T / NA - m - / Wb m -2 [Total 5] 7 (a) ( ev) is the work (done) / energy gained / transformed by an electron travelling / accelerated through / across a p.d. / voltage of V (Allow a proton instead of an electron) ev = (J) (Ignore omission of unit but NOT C ) (b) energy, photon and (photo)electron respectively 3 (Allow momentum / charge instead of energy for the first marking point) (c)(i) energy of photon = work function energy / hf = φ φ = / / φ = φ = (J) (J) φ = / φ = 3.88 (ev) 3.9 ev Possible ECF A (ii) No (photo)electrons Photon energy is less than the work function (energy) / The frequency (of the radiation) is less than the threshold frequency / Photons heat the metal C A [Total ] 8 (a) (b)(i) h λ = / mv h λ = M p λ = wavelength, h = Planck constant, m = mass (of particle) and v = speed / velocity O p = momentum A Neutrons have no charge / Neutrons experiences no electrical forces (ora) (ii) = / mv / mv = (kgms - ) C v = / ( ) / v = / C v = (ms - ) (Allow use of m n = kg) A [Total 6]

2822/01 Physics A: Electrons and Photons. June Mark Scheme

2822/01 Physics A: Electrons and Photons June 2004 Mark Scheme The following annotations may be used when marking: X = incorrect response (errors may also be underlined) ^ = omission mark bod = benefit