C A R I B B E A N E X A M I N A T I O N S C O U N C I L

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1 C A R I B B E A N E X A M I N A T I O N S C O U N C I L REPORT ON CANDIDATES WORK IN THE CARIBBEAN SECONDARY EDUCATION CERTIFICATE EXAMINATION MAY/JUNE 2009 PHYSICS Copyright 2009 Caribbean Examinations Council St Michael Barbados All rights reserved.

2 - 2 - PHYSICS GENERAL PROFICIENCY EXAMINATION MAY/JUNE 2009 GENERAL COMMENTS This year 11,645 candidates wrote the examination compared with 10,165 in This represents an increase of 14.6 per cent in candidature. Approximately 77 per cent of the candidates obtained acceptable grades, Grades I III. The standard of work seen from most of the candidates in this examination was generally good. Candidates, however, needed to show better mathematical skills in areas such as scientific notation, solving equations and simple geometry. More emphasis must be placed on using mathematical skills in studying Physics. Although School-Based Assessment moderation showed acceptable performances, candidates experienced difficulty in writing up experiments not accessed via the School Based Assessment. Teachers are encouraged to make the Physics course as practical as possible while satisfying the requirements of the School-Based Assessment. The more direct experience candidates gain will result in better understanding and retention. Paper 01 Multiple Choice The performance in this year s multiple choice paper improved over that of June This year, the average mark was (56.18 per cent) out of 60, with a standard deviation of Question 1 Paper 02 Structured Questions/Essay Type This question tested candidates knowledge of radioactivity. The overall performance revealed that 14 per cent of candidates obtained a score of 13 or more out of a possible 25 marks. The majority of the candidates were in the lower quartile of the distribution of marks. Candidates were able to correctly plot the graph and explain the term half-life. However, the following weaknesses were identified. - Inability to determine the half- life of a radioactive sample from a graph of count rate versus time - Failure to calculate the number of half-lives that can be obtained at 425 seconds interval - Omitting to estimate the count rate after a certain number of half-lives elapsed - Non-recognition of activity versus time graph being curved as opposed to linear

3 - 3 - Question 2 This question tested candidates ability to differentiate between scalar and vector physical quantities. The question further tested their ability to draw velocity time graphs and calculate distance travelled. The question was well answered. However, candidates are reminded of the fact that the area under a velocity time graph gives the distance travelled. In addition, it was of concern to note that a few candidates wrote: Distance travelled = velocity x time = 30 5 = 150 m whereas the correct response should have been Distance travelled = average velocity x time = [(30 + 0)/2] x 5 = 75 m. Question 3 (1) This question tested candidates knowledge of the fundamental principles of light. Many candidates avoided the question or gave inadequate responses. (2) The point x on the diagram was not adequately labelled. Candidates were not penalized for this oversight on the question paper. (3) Candidates must be reminded that as light travels from hotter (less dense) air to cooler (more dense) air it bends towards the normal. In this situation the air between the surface and the observer gradually gets more dense, therefore the light ray going from the surface to the observer would be gradually bending. Question 4 This question tested candidates ability to calculate work done and energy. question challenging. Candidates found this The work done against gravity = force x distance. Most candidates applied this formula but could not identify force with weight (mass times acceleration due to gravity). To calculate the increased speed, candidates needed to calculate the potential energy change at the end of the descent. Following that, they needed to obtain 90 per cent of that potential energy change to obtain the work done against friction. The remaining energy or the 10 per cent would now be the kinetic energy

4 - 4 - that the rider and cycle must have. Equating this to would enable the speed calculation to be made. Candidates ought to have recognized that the average rate of energy conversion in Part (iii) was simply a power calculation (power = energy/time). Question 5 Candidates found this question challenging. This question tested the candidates knowledge of electricity and magnetism. The stimulus material for this question appeared to initiate and direct candidates to give the desired responses. Over 50 per cent of the candidates earned more than half of the total possible marks. Most candidates were able to sketch the magnetic field and calculate the current and the number of turns. However, candidates failed to recognize that the answer required was the diode or a rectifier. Candidates must be reminded that efficiency is based on power or work or energy ratios and not on voltage ratio alone or current ratio alone. Question 6 The question tested the candidates knowledge of Thermal Physics. This question was not well answered as candidates were unfamiliar with the method of mixtures for finding the specific latent heat of fusion of ice. One popular erroneous statement was heat energy lost by ice is gained by water. Candidates generally knew the formulae such as E = mc and E = ml but had difficulty in applying them in the appropriate respective stages in Part. Candidates are urged to practise responding to these types of questions to gain a greater understanding of the processes involved. General comments and recommendations Candidates needed to have the experience of performing the experiment and writing in an acceptable manner. Appropriate units are to be used at all times.

5 - 5 - Paper 03- School-Based Assessment (SBA) School-Based Assessment is an integral part of the students preparation for the final examinations. It also contributes 20 per cent of the final marks. Teachers are expected to work together at each centre to have a common core of 16 activities. Other minimum requirements are: (c) (d) (e) Syllabus coverage 10 topics Marking of each skill 4 times Graphs 5 times Detailed mark scheme breaking down each of the criteria to 1 mark. Marks and remarks in all books. (f) Books per centre to submit 5 The quality of teachers marking was generally good. Teachers marking was consistent and reflected the standard expected. For many centres the standard of the SBA has improved. This was evidenced by the high percentage of centres with - adequate syllabus coverage and the total number of activities - assessment of each skill at least four times - good graph work - good standard of practical exercises - good ORR - good A/I results. Recommendations (c) The use of standard (traditional) laboratory exercises is inappropriate for assessing the Planning/Design skills. Table of contents should clearly identify the 16 assessments by skill. Clear instructions and a detailed mark scheme must be submitted for each assessment.