Infra-Red Radiation. Mark Scheme. Save My Exams! The Home of Revision. Exam Board. Page 1. Score: /47. Percentage: /100

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1 Infra-Red Radiation Mark Scheme Level Subject Exam Board Unit Topic Difficulty Level Booklet GCSE Physics AQA P Infra-Red Radiation Gold Level Mark Scheme Time Allowed: 47 minutes Sce: /47 Percentage: /00 Page

2 M.(a) 4200 J / kg C allow 2 marks f crect substitution ie 6930 = c 5.0 answers of crectly calculated answer from crect substitution of increct temperature change identification of temperature change ie 5 C gain mark accept J / kg K 3 (b) (in a metal) free electrons to gain full credit the answer must be in terms of free electrons gain kinetic energy accept move faster (free electrons) transfer energy to other electrons / ions / atoms do not accept particles by collision allow a maximum of 2 marks f answers in terms of atoms / ions / particles gaining kinetic energy vibrating faster / me transferring energy by collisions (c) (air) particles spread out (which causes the) air to become less dense / expand do not accept particles become less dense (so the) warm air rises do not accept heat rises Page 2

3 particles rise is insufficient (d) large surface area igne references to type of metal external conditions black / dark (colour) [3] M2. (a) (i) refraction accept refracted reflection, diffraction and dispersion are increct (ii) to check rise in temperature (of other thermometers) was due to the (different wavelengths of) light accept as a control / comparison to measure room temperature is insufficient (iii) any two from three: different colours produce different heating effects / (rises in) temperatures red light produces the greatest heating effect / (rise in) temperature violet produces the least heating effect / (rise in) temperature all colours produce a greater heating effect than outside the spectrum an answer the longer the wavelength the greater the (rise in) temperature the lower the frequency the greater the (rise in) temperature gains both marks 2 Page 3

4 (b) move a thermometer into the infrared region / just beyond the red light allow use an infrared camera / infrared sens the temperature increases beyond 24( C) accept temperature higher than f the red light (c) v = f λ accept accept allow mark f crect substitution ie = λ 2 (d) at night the surroundings are cooler accept at night the air is colder there is no heat from the Sun is insufficient at night there is a greater temperature difference between people and surroundings (so surroundings) emit less infrared (than in daytime) accept camera detects a greater contrast gives larger difference in infrared emitted (between people and surroundings) [0] Page 4

5 M3. (a) (i) conduction (ii) free / mobile electrons gain (kinetic) energy accept free / mobile electrons move faster free electrons collide with other (free) electrons / ions / atoms / particles an answer in terms of atoms / particles gaining (kinetic) energy (and) colliding with / vibrating and passing energy to other atoms / particles gains mark only answers in terms of heat particles negate (iii) convection (b) (i)this mark only sces if a crect pair is chosen and a crect reason given A and C both required and none other B and D both required and none other only one (independent) variabledifferent shapes but the same colour accept only the shape changes (ii) B radiates heat faster converse answer in terms of A gains full marks B is a better emitter (of heat) but B has a smaller (surface) areab has a smaller (surface) area: volume ratio allow 2 marks f both lose the same quantity / amount of heat in the same time both have same rate of heat loss Page 5

6 allow mark f both lose the same quantity / amount of heat (iii) any one from: transfer a lot of heat (too rapidly) water temperature drops too rapidly accept (significantly) me heat will be lost from the first radiat water too cold f the next radiat mention of absption of heat negates mark [8] M4. (a) conduction do not accept conduct (b) the freezer both parts needed greater temperature difference (between freezer and room) do not accept because it is the coldest (c) any two from: po absber of heat / radiation accept does not absb heat po emitter of heat / radiation is neutral reflects heat / radiation (from room away from fridge-freezer) reduces heat transfer into the fridge-freezer reduces power consumption of fridge-freezer do not accept it is a bad conduct / good insulat 2 Page 6

7 [4] M5. (a) ions / electrons gain (kinetic) energy accept atom / particles / molecules f ion accept ions vibrate faster accept ions vibrate with a bigger amplitude accept ions vibrate me do not accept ions move faster (free) electrons transfer energy by collision with ions energy transferred by collisions between vibrating ions (b) move faster take up me space do not accept start to move / vibrate (warmer) water expands becomes less dense (than cooler water) do not accept answers in terms of particles expanding warm water rises (through colder water) colder water falls to take its place (c) transfer of energy by waves / infrared (radiation) accept rays f waves do not accept transfer of energy by electromagnetic waves igne reference to heat [6] Page 7

8 M6. (a) convection air is heated by the burner / particles gain energy air expands / particles move about me / particles move faster air becomes less dense / particles are me spread out air rises / particles rise - not heat rises air from C moves into the heater / particles from C move into the heater to replace it / them any four f mark each 4 (b) (i) radiation f one mark (ii) black surface radiates / emits well (allow absbs and emits well) (allow comparison with shiny / white surfaces) large surface area needed high temperature (of the lumps) any one f mark [6] Page 8