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3 pm Jan 22, 2013

CBSE Board physics examination

As part of the IBNLive-Topper chat series, Shruti Gupta, physics teacher, will interact with students who will appear for the 2013 CBSE Board examinations which start from March 1. Parents and teachers can also benefit from her tips.
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50 questions answered | 14 questions pending
  • what is refractive index Asked by: ansh
  • Shruti Gupta Refractive index is defined as the ratio of the speed of light in a vacuum to that in a given medium.
  • Alight string pasing over a smooth light pulley connects 2 blocks of masses m1 and m2(vertically). If the acceleration of system is g/8. Then ratio of masses is---- Asked by: vandna
  • Shruti Gupta m2a=m2g-T m1a=T-m1g by solving we get:a=(m2-m1)g/(m1+m2) now putting a=g/8 and solving we get: m1/m2=7:9
  • what is quantum theory? could you suggest a site which could explain this? Asked by: Manisha Behera
  • Shruti Gupta As of now can go through :http://www.thebigview.com/spacetime/quantumtheory.html for basics
  • how rainbow form? Asked by: ansh
  • Shruti Gupta A rainbow is always formed in a direction opposite to that of the Sun. The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colours reach the observer's eye.
  • we see sky blue because we see it threw oxygen Asked by: ansh
  • Shruti Gupta no because blue light is scattered the most so sky appears blue.
  • how to fbd in constraint reltions? Asked by: vandna
  • Shruti Gupta These are not in cbse syll.
  • why this is written on back view mirror in car that object is closer than they appear but convex mirror form images near to the mirror in comparision to object Asked by: ansh
  • Shruti Gupta because in case of convex mirrors the image distance is lesser than the object distance.
  • What is a thyristor( SCR) ? Asked by: sairam
  • Shruti Gupta A four-layered semiconductor rectifier in which the flow of current between two electrodes is triggered by a signal at a third electrode.
  • is principal of reversibility will come in 10th cbse board exam Asked by: ansh
  • Shruti Gupta Yes it is.
  • what is refractive index??? Asked by: pooja
  • Shruti Gupta Refractive index is defined as the ratio of the speed of light in a vacuum to that in a given medium.
  • an object 5 cm high is placed at a distance of 10cm from a convex mirror of radius of curvature 30 cm find the nature, position and size of the image. Asked by: Ishant
  • Shruti Gupta h=5cm u=-10cm f=15cm 1/v + 1/u = 1/f Substituting the values and solving we get v = 6 cm i.e., the image is virtual and erect. Magnification, m = -v/u = h'/h -6/-10 = h'/5 Height of image, h' = 3 cm i.e. diminished image
  • how shoul i balance my time table if i start at 6 pm. Asked by: vandna
  • Shruti Gupta that depends upon individual.Its pretty decent.
  • is image only form when 2 reflected ray intersect ??if yes then how image form in concave mirror when object is placed at focus and reflected ray are parallel and make object at infinity but they are parallel and do not intersect then how image form Asked by: ansh
  • Shruti Gupta images are not only form when 2 reflected ray intersect, it also formed when rays diverge after reflection or refraction .They appear to come from one point....in this case they appear to meet at large distance.
  • If a ray of light is incident on the mirror such as angle of incidence is equal to the angle of reflection is equal to zero degrees then the packets of photons carrying light should get destroyed ? then why it doesnt so ? Asked by: Akash
  • Shruti Gupta if angle of incidence=angle of refl then why sh the photonts get destroyed..they d go by the same path after reflection
  • define inertial and non inertial frame of reference in detail with example? Asked by: vandna
  • Shruti Gupta Inertia frames of reference are those reference frames in which Newton’s laws are valid. They are non-accelerating frames. Non-inertial frames of reference are those reference frames in which Newton’s laws are invalid. They are accelerating frames.
  • Why do they take 340m/s as the standard speed of sound and why not 344m/s? Asked by: Dharun Viknesh
  • Shruti Gupta Speed of sound varies with different factors, in general for normal condition it is sometimes taken or given in the problem as 340m/s
  • block of mass m is stationary wrt wedge.Normal force exerted by wedge on the block is--- Asked by: vandna
  • Shruti Gupta Mg cos theta
  • Ma'am please help me in making a good time table I am really confused how to divide hours to get best of it. Asked by: Akash
  • Shruti Gupta First and fore most thing you have to keep in mind is to keep a balance between revision and practice of questions(different typesof) and also keep some time for practicing sample papers.
  • what is the main reason for occurence of dispersion of light and scattering of light? Asked by: sheetal
  • Shruti Gupta As white light comprises of seven colours,and different colours have different refractive index for different materials so they bend differently as white light enters a medium from another.So dispersion occur.
  • what are other types of convex lens other than biconvex? Asked by: Amisha
  • Shruti Gupta plano-convex lens and concavo-convex lens.
  • write correct order of fundamental forces (strongness)? Asked by: vandna
  • Shruti Gupta Nuclear force is the strongest.Gravitational force is the weakest.
  • My daughter had not done her preboard well. Wish she be able score above 90% in the last one month? Asked by: sameera
  • Shruti Gupta Can be done with shear determination , practice and hard work.Perfect planning is also required.
  • if displacement x of a particle of mass m is directly proportional to time ,net force acting on it is--------------- Asked by: vandna
  • Shruti Gupta x = kt dx/dt = k Derivative of dx/dt (i.e. acceleration) will be zero since it is a constant. F = ma = 0
  • is the board paper strictly according to the sample paper blue print please explain?? Asked by: bhanu
  • Shruti Gupta If you are in class xii then yes but for class x it may be different as board is not following any blue print as such from this year.
  • what is angle of deviation &spectrum??? Asked by: ansh
  • Shruti Gupta The angle of deviation is the angle between the original incident ray and the emergent ray. Spectrum is a band of colors, as seen in a rainbow, produced by separation of the components of light by their different degrees of refraction according to wavelength.
  • explain laws of conservation of momentum.with example Asked by: vandna
  • Shruti Gupta watch this episode to clear your doubts: http://www.topperlearning.com/student/topic/MjQ4/CBSE-Class%20IX-Physics-Force%20and%20Laws%20of%20Motion-Conservation%20of%20Linear%20momentum
  • explain laws of conservation of mass. Asked by: pragya
  • Shruti Gupta The law of conservation of mass states that the mass of an isolated system will remain constant over time.
  • Is additional excercise form ncert text book important? Asked by: kavya
  • Shruti Gupta Yes they are very good especially if you are preparing for competitive.
  • My teachers ask me to only study her notes and asked me to do numericals from the text book. Is that fine? Asked by: sandhya
  • Shruti Gupta It is good. But you should not practise only from one book.Should try to solve more after understanding the concept. Also try to practice answering questions.
  • Define: Atmospheric Refraction, Power of Accommodation. Asked by: Prithivi Raj
  • Shruti Gupta Atmospheric refraction is the phenomenon of bending of light on passing through earth's atmosphere. Power of accomodation is the ability of the eye to observe distinctly the objects situated at widely different distances from the eye.
  • How to find out the focal length of the lens if only the power of lens is given? Asked by: sheetal
  • Shruti Gupta power=1/focal length in meter
  • Does the Sample Question papers helps for Studying harder questions? Asked by: Prithivi Raj
  • Shruti Gupta Yes sample papers are always good for practice, but for harder questions one should practice from more and more sources.
  • What is the important book from which we study in exam. Asked by: Ishant
  • Shruti Gupta It depends on the class you are studying in. However, the NCERT book should be followed first.
  • Why does in a prism all colour disperse whereas in rectangular glass slab it doesnt? Asked by: Akash
  • Shruti Gupta Rectangular slab can be considered as two prisms kept in contact with each other , one in inverted position with another.As we know that the dispersed colours of light recombine as they pass through two prisms , last one kept in inverted position, in case of rectangular glass slab we do not see light dispersing.
  • How to score well If I start from now ? What topics should I study ? Asked by: Aryan
  • Shruti Gupta First, a clear understanding of the basics is necessary. Then get on to practicing various questions and sample papers. You may also visit www.topperlearning.com. You must study all the topics to get flying colours.
  • what kind of questions may be asked in value based questions Asked by: bhanu
  • Shruti Gupta Related to everyday life or real life.
  • can a concave mirror through a beam of light and burn a paper Asked by: Anurup Mohanty
  • Shruti Gupta concave mirror also can focus all light coming at one point and hence can burn papers.
  • define reflection, refraction,diffraction, dispersion Asked by: sheetal
  • Shruti Gupta Reflection- bouncing back of light in the same medium on striking the surface of any object. Refraction- The change in the path of light in going from one medium to another. Diffraction- The process by which a beam of light or other system of waves is spread out as a result of passing through a narrow aperture or across an edge. Dispersion- Splitting of white light into its constituent seven colours on passing through a glass prism.
  • how to read ncert books to clearly understand everything? Asked by: Amit Kumar Singh
  • Shruti Gupta Study each line and try to understand the basics from the very first day.
  • Please tell me what questions are likely to come from diffraction topic Asked by: bhanu
  • Shruti Gupta you need to understand: 1. conditions 2. diffraction pattern and derivation of fringe width 3. intensity graph of fringes 4. differences between diffraction and interference 5. numericals
  • Do we need to study the Structure of Eyes in Detail? Asked by: Prithivi Raj
  • Shruti Gupta Yes you have to understand the function of each part .
  • Do we need to study the rocket propulsion in 11 class in Detail? Asked by: vandna
  • Shruti Gupta NO it is not in CBSE syll.
  • How will frequency of small oscillation of a simple pendulum change when it move vertically upward with acceleration a. Asked by: vandna
  • Shruti Gupta As time period of simple pendulum is =2pi sq root of l/g, so as the pendulum move vertically upward with acceleration a, its effective acceleration becomes=g+a so the time period now will be:2pi sq root of l/g+a, so the time period will be lesser and frequency will be more.
  • Now that there is only one month left what exactly should the student be doing in the coming month? Asked by: priya
  • Shruti Gupta 1. plan out properly. 2. Fix your routine such that every day what ever you plan for studying next day or the same day you should practice numericals or application based questions from the same. 2. after 1 week you should do random practice of questions, derivations and numericals of different types from the chapters you revised that week.
  • My daughter has not done her revisions or her preboard that well. Can she prepare in the last one month and score above 90%? Asked by: sameera
  • Shruti Gupta She can score better by devoting good time to the subject, first grasping the concepts of the textbook and then practicing more problems to make the understanding firm.
  • what is principal of reversibility? Asked by: ansh
  • Shruti Gupta The principle of reversibility states that light will follow exactly the same path if its direction of travel is reversed.
  • How to score good with derivations. There are lot of derivations so how to get through them? Asked by: pulkitt
  • Shruti Gupta The key is- understand the basic underlying principles and practice by writing.
  • Does books like exam idea help or should we keep studying the ncert books ? Asked by: Sushmitha
  • Shruti Gupta NCERT book is a must-read. Once you are clear with the basic concepts, you may refer to any reference book to practice more.
  • Does going through the text book help or going through previous paper will help to improve the marks ? Asked by: Madhmita
  • Shruti Gupta Text books should be read to understand the concept better. Also, previous year papers give an idea about how the paper is set and what kind of questions are asked in the exam.
  • does numaricals in physics text book alone fetch us full marks in numricals part in physics paper?? Asked by: Nikhil Varma
  • Shruti Gupta No for numericals you have to practice more and more problems, rather practical/situation based application type problems.

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Shruti Gupta
Physics teacher