Tuesday 31 December 2013
Cambridge IGCSE Physics 2012 (0625-11+13) - Waves
Candidates found Question 21 (31% correct) and Question 40 (35% correct) the most difficult on the paper.
Question 21
(click to enlarge picture)
Many candidates did not appear to understand what is meant by the term ‘wavefront’ and there was
evidence of widespread guessing.A wavefront is the locus of points having the same phase: a line or curve in 2d, or a surface for a wave propagating in 3d.
Based on the definition, the answer must therefore be option 'C'. While 'A' being the direction of wave motion; 'B' being the wavelength interval of a wave; and 'D' being the reflecting surface.
Question 40
(click to enlarge picture)
In this question on nuclear structure more than half the candidates opted for 'B', either failing to notice that the question concerned a nucleus rather than an atom, or in the mistaken belief that nuclei contain electrons.
A nuclide (from nucleus) is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state.
Noticed that candidates always fail to learn their definitions well, hence, led to poor understanding. This question-type can easily be handled using pure definition approach.
0625-13 MCQ
Question 21 (28% correct) and Question 24 (36% correct) were the most difficult on the paper.
Question 21
A nuclide (from nucleus) is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state.
Noticed that candidates always fail to learn their definitions well, hence, led to poor understanding. This question-type can easily be handled using pure definition approach.
0625-13 MCQ
Question 21 (28% correct) and Question 24 (36% correct) were the most difficult on the paper.
Question 21
(click to enlarge picture)
Question 24
(click to enlarge picture)
A wavefront is the locus of points having the same phase: a line or curve in 2d, or a surface for a wave propagating in 3d.
Based on the definition, the answer must therefore be option 'B'. While 'A' being the amplitude of wave motion; 'C' being the wavelength interval of a wave; and 'D' being the wave edge.
This year's candidates were not taught well in waves section.
Question 24
This question required knowledge that a ray of light travelling from water to a less dense medium (air) would
be partially reflected, as well as being refracted. Most candidates did not know that some reflection would
occur for angles of incidence below the critical angle.
Total internal reflection is a phenomenon that happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected. The critical angle is the angle of incidence above which the total internal reflectance occurs. This is particularly common as an optical phenomenon, where light waves are involved, but it occurs with many types of waves, such as electromagnetic waves in general or sound waves.
When a wave crosses a boundary between materials with different kinds of refractive indices, the wave will be partially refracted at the boundary surface, and partially reflected. However, if the angle of incidence is greater (i.e., the direction of propagation or ray is closer to being parallel to the boundary) than the critical angle – the angle of incidence at which light is refracted such that it travels along the boundary – then the wave will not cross the boundary and instead be totally reflected back internally. This can only occur where the wave travels from a medium with a higher refractive index (n1) to one with a lower refractive index (n2). For example, it will occur with light when passing from glass to air, but not when passing from air to glass.
This question demands a higher standard of care. Candidates are advised to read slightly beyond current syllabus.
Exams Question Paper Source:
Recommended books to buy to solidify these key concepts:
Monday 30 December 2013
DISCLAIMER
Local Regulatory Restrictions
While this blog can be accessed worldwide, not everyone should or is invited or asked to access this blog. As such, the information provided and the products and/or services accessible through this blog are respectively only intended for use by any person in any country where such access and/or use would not be contrary to local law or regulation. If you choose to access this blog from any location then you do so on your own initiative and at your own risk. It is your sole responsibility to ascertain the terms of use and comply with any local law or regulation to which you are subjected to.
Use of the Blog
The access and use of any product, service or links on this blog is expressly subject to the terms of this Disclaimer and the Terms of Use, which are to be read together. If you do not agree with any part of this Disclaimer and/or the Terms of Use, you must immediately discontinue your access and any use of this blog. This Disclaimer and/or the Terms of Use may change from time to time without notice. By continuing to access and/or use any information/ products/services available on or through this blog, you are agreeing to be bound by the current version of this Disclaimer. All authors and commenters, resident or guest, shall not in any event be liable for any damages or injury arising out of your access to, or inability to access, this blog or from your reliance on any information provided here. The authors and commenters disclaim any and all liability for direct, indirect, incidental, consequential, punitive, and special or other damages, lost opportunities, lost profit or any other loss or damages of any kind. This limitation includes any damage or virus, which may affect your computer equipment.
General Information and Circulation
The information and materials provided here, whether or not provided on the blog, on third party websites, in marketing materials, newsletters or any form of publication are provided for general information and circulation only.
No Recommendation or Advice
None of the information contained here constitutes an offer (or solicitation of an offer) to buy or sell in any currency, product or financial instrument, to make any investment, or to participate in any particular trading activity. The authors and commenters do not take into account of your personal objectives, specific goals, specific needs or situation and makes no representation and assumes no liability to the accuracy or completeness of the information provided here. The information and publications are not intended to be and do not constitute any advice or recommendation of any sort offered or endorsed by the authors and commenters. The authors and commenters also do not warrant that such information and publications are accurate, up to date or applicable to the circumstances of any particular case. Any expression of opinion (which may be subject to change without notice) is personal to the author and the author makes no guarantee of any sort regarding accuracy or completeness of any information or analysis supplied. The authors and commenters are not responsible for any loss arising from any decisions based on any perceived recommendation, forecast or any other information contained here. The contents of these publications should not be construed as an express or implied promise, guarantee or implication by the authors and commenters that clients will profit or that losses in connection therewith can or will be limited, from reliance on any information set out here.
Third Party Services – Linked Sites and Banners
On this blog, other companies may advertise or may have their products and/or services accessible through links or banners. The authors and commenters are not responsible/liable and does not accept any responsibility/liability for the contents of any such banners, linked sites or for the products and/or services offered/accessible from such banners or linked sites. If you decide to act on any such information or offers, you do so entirely at your own risk. In particular you agree that if you should access such linked sites through clicking on the relevant site link(s) on this blog, you will then be leaving this blog and be proceeding on to the linked site where you will be subject to the terms of that linked site.
Copyrights
"The distinction between fair use and infringement may be unclear and not easily defined. There is no specific number of words, lines, or notes that may safely be taken without permission. Acknowledging the source of the copyrighted material does not substitute for obtaining permission."
On this blog, any noted copyrighted materials are properties of their respective copyright owners.
Duplication or sale of all or any part of these copyrighted materials is not permitted, except that material may be duplicated by you for your personal research use or educational purposes in electronic or print form, in accordance with the terms of the copyright, designs and patents act of your country. Permission for any other use must be obtained from the copyright owners. Electronic or print copies may not be offered, whether for sale or otherwise, to any third party. Links to materials on other servers should not be construed as a claim over them.
Fair Use
is a limitation and exception to the exclusive right granted by copyright law to the author of a creative work. In most copyright laws, fair use is a doctrine that permits limited use of copyrighted material without acquiring permission from the rights holders. Examples of fair use include commentary, search engines, criticism, parody, news reporting, research, teaching, library archiving and scholarship. It provides for the legal, unlicensed citation or incorporation of copyrighted material in another author's work under a four-factor balancing test.
No Endorsement of Third Party Services
Reference to any third party information (including information provided by a third party or accessible through any linked site), product, process, or services at this blog or any linked site is not an express or implied endorsement by the authors and commenters of the same.
Subscribe to:
Posts (Atom)