Saturday, October 30, 2010

Hints of lightweight dark matter particle found in space

Hints of a lightweight dark matter particle have been found in the gamma-ray glow at the Milky Way's heart. The particle's apparent mass lines up with tentative signals of dark matter in two direct-detection experiments on Earth, but other researchers caution that conventional sources – such as pulsars – may be responsible for the gamma-ray light instead.


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Entrance Exam for Sainik Schools : Get Help and Guidance Here


a. Written Test : The test will be held on Third Sunday of Feb every year. details are as follows: Class VI: i. Mathematical knowledge Test & Language Ability Test. ii. Intelligence Test. The test can be taken in English or Hindi or Malayalam.

Class IX: i. Mathematics & Science ii. English & Social Studies The test can be taken in English or Hindi or Malayalam except serial No. 2 English. However the question papers will be in English only. b. The syllabus and question pattern given are subject to changes from time to time. c. Interview & Medical Test: The boys who qualify in the written test will be required to appear at a later date before a selection Board for an Interview & Medical Test. Prospectus, Application form and Model question paper can he obtained from the Principal, Sainik School, Kazhakootam by post on payment of the prescribed cost mentioned below, by sending a crossed demand draft, payable at Trivandrum drawn in favour of Principal, Sainik school, Kazhakootam, Trivandrum.


1. The Medical Examination of candidates for admission to Sainik School will be carried out by a Medical Board

2. It is not possible to lay down precise standard for height, weight and chest measurements for these candidates. But the Medical Board will be guided in its assessment by the Physical standards laid down for candidates for admission to National Defence Academy. Height and to an extent weight are constitutional qualities which are largely governed by heredity. Therefore candidate whose parents are short statured and below normal weight may not eventually attain the minimum standard height and weight required for the Armed Forces. This point should therefore he borne in mind by the parent/guardians of such candidates before they seek admission for their children/wards. The important facts concerning health are given below: -

3. Visual Standards Distant Vision (uncorrected) Standard I 6/6 (Both eyes) Distant Vision Standard II Better eye worse eye 6/18 6/18 Correctable to 6/6 Correctable to 6/9 The minimum acceptable visual standard for admission to Sainik School will be Standard II Colour perception: CPI (MLT)

Note a. i. Myopia not to exceed minus 1.5 D including astigmatism

ii. Manifest Hypermetropia not to exceed plus 2.5 D sph including astigmatism

iii. Fundus & Media to he healthy with no changes of myopia

iv. Visual Fields-to be full in each eye.

v. Binocular vision and stereopsls must be good

b. The above will have to he certified by a State Employed Ophthalmologist in advance of boy’s arrival for admission.

c. There is no squint or morbid condition of the eye or of the lids, which is liable to a risk of aggravation or recurrence.

4. It will also he ensured that:

a. There is no evidence of weak constitution, malformations or obesity, there is no evidence of heart murmur.

b. There is no maldevelopment or impairment of function of the bone of joints.

c. There is no impediment of speech.

d. There is no malformation of the head, deformity from fracture or depression of the bones of the skull

e. There is no impaired hearing, discharge from or disease of either ear unhealed perforation of tympanic membranes or signs of acute or chronic suppurative otitis media or evidence of radical or modified radical mastoid operation. (Note: - A soundly healed perforation without any impairment of the drum and without impairment of the ring should not he a case of rejection)

f. There is no disease of nasopharynx.

g. There are no enlarged glands in the neck and other parts of the body and that thyroid gland is normal.

h. Knock-knee and flat foot are not eligible for admission.

i. Phimosis and caries teeth are not eligible for admission

N.B. Scars of operations for the removal of tuberculosis glands are not a cause for rejection provided there has been no active disease within the preceding 5 years and the chest is clinically and radiologically clear.

j. There is no disease of the throat, plate, tonsils or gums or disease or injury affecting the normal function of either mandibular joint.

k. There is no sign of functional or organic disease of the heart and blood vessels.

l. There is no evidence of pulmonary tuberculosis or previous history of this disease or any other chronic disease of the lungs

m. There is no evidence of any disease of the digestive system including any abnormality of the liver and spleen.

n. There is no hernia or tendency there to.

o. There is no hydryocele or definite varicocele or any other disease or defect of the genital organs.

N.B. A candidate who has been operated for hydryocele will be accepted if there are no abnormalities of the cord and testicle and there is no evidence of filariasis.

p. There is no fistula or fissure of the anus or evidence of haemorrhoids.

q. There is no disease of the Kidneys. Cases showing albuminuria or Glycosuria will not be accepted.

r. There is no disease of the skin, unless temporary or trivial. Scars which by their extent or position cause or are likely to cause disability or marked disfigurement are a cause for rejection.

s. There is no active latent, or congenital disease.

t. There is no history or evidence of mental disease. Candidates suffering from epilepsy incontinence of urine, or enuresis will not he accepted.

N.B. Remedial operations are to he performed prior to entry. No guarantee is given for ultimate acceptance and it should he clearly understood by the candidate that the decision whether an operation is desirable or necessary, is one to be made by his private medical adviser. The school will accept no liability regarding the result of operation or any expense incurred.

Tuesday, October 12, 2010

Pattern of Half Yearly Exam for Class XI

In most schools NCERT Textbook Vol – I will be taken as the portion for Half yearly exam.

The mark distribution as per CBSE  is like this

1 mark x 8 questions  = 8 marks

2 marks x 10 questions  = 20 marks

3 marks x 9 questions  = 27 marks

5 marks x 3 questions = 15 marks


There will about 15 marks questions classified as Higher Order Thinking Skills (HOTS)Questions. These are questions which require a thorough understanding of the topic and the student must be able to apply the learnt concepts to different familiar or unfamiliar situations. (The students who solve the additional exercises from NCERT  text book will not find these difficult)

There will be about 10 to 15 marks questions classified very easy. The rest will be average level.

This means that if you are an average student with thorough revision, you can easily score 85% marks in Physics theory.

SO, Plan well, learn well, Success is yours.

Best Wishes.

Physics Revision Help for Half Yearly Exam Class XI CBSE & KVS

3 and 5 Marks Questions

It is very much essential to completely solve all the exercises (including the additional exercises) given in NCERT text book.

  1. What are errors? Describe the propagation of errors in addition subtraction multiplication and division.

  2. What do you mean by the principle of homogenity of dimensions? Describe the applications of dimensional analysis.

  3. Derive the equations of uniformly accelerated motion (graphically)

  4. Define projectile motion. Derive expression for Time of Flight, Horizontal Range and maximum height of a projectile.

  5. Derive an expression for the trajectory of a projectile.

  6. Show that there are two possible angles of projection for obtaining the same range.

  7. Derive an expression for centripetal acceleration in Uniform Circular motion.

  8. Derive F=ma from Newton’s second law of motion.

  1. State and explain Newton’s laws of motion.

  2. Show that Newton’s I law and Third law can be derived from II law.

  3. A light inextensible string with ends connected to two unequal masses runs over a frictionless pulley and is free to move. Derive an expression for the acceleration of the masses and the tension in the string.

  4. State Impulse – momentum principle and explain its applications.

  5. Why does a cricket player pulls his hands backwards while taking a catch? Describe similar situations of the principle based on which he does so.

  6. Explain the cause of friction.

  7. Why friction is called a necessary evil?

  8. Describe the different methods used to reduce friction.

  9. Derive an expression for the maximum safe velocity of a car on a level road.

  10. What do you mean by banking of roads at curves? Derive and expression for the maximum safe velocity of a car on a banked road and hence derive the velocity at curve on a banked road for minimum wear and tear.

  11. Derive an expression for the minimum horizontal velocity to be given to a ball hanging vertically from a point so that it is able to just complete a vertical circular path.

  12. Derive expression for the tension in a string at the top and bottom position while a body attached to its end describes a vertical circle.

  13. State and prove work – Kinetic energy theorem

  14. State the principle of conservation of energy. Show that the total mechanical energy of a body falling freely from a height remains constant throughout its motion.

  15. Distinguish between elastic and inelastic collisions

  16. Show that there is always a loss of kinetic energy in ordinary inelastic collisions.

  17. Derive an expression for the velocities after elastic collision between two bodies.

  18. Discuss elastic collision in two dimensions

  19. Derive the relationship between momentum and kinetic energy.

  20. Two particles of different mass have the same momentum; which one has greater kinetic energy - the light body or the heavy body?

  21. Two particles of different mass have the same kinetic energy; which one has greater momentum - the light body or the heavy body?

  22. Define radius of gyration.

  23. Define moment of inertia.

  24. Derive an expression for the centre of mass of a two particle system.

  25. Derive an  expression for the rotational kinetic energy of a rigid body

  26. Derive an  expression for the angular momentum of a rigid body

  27. State the principle of conservation of angular momentum and explain its applications.

……………… Will be updated soon with more

Saturday, October 9, 2010

AISSCE 2008 Question Paper and Solution

CBSE students can download the AISSCE 2008 Question Paper set I with solution here. Please follow the link given below.

aissce physics 2008 qp and sol

CBSE (AISSCE) Physics 2010 Question Paper set 2 outside Delhi

Please click the link below to download Physics Question Paper set 2 of AISSCE 2010 conducted by CBSE. Solving question papers is one of the best ways of preparing to score good marks in any exam.

AISSCE Physics 2010 QP set2

Current Electricity : Some important Questions and Answers

Current electricity is one of the interesting as well as scoring chapter for the students of Class XII. Please find below a collection of questions and answers commonly asked in various Board Exams

current electricity

Thursday, October 7, 2010

A short introduction to Optics and the Nature of Light


LIGHT is a form of energy which causes the sensation of vision. Optics is the branch of Physics which studies the nature of light and the various phenomena associated with it.

Nature of Light

The nature of light was not at all thought until Newton attempted on it.

Newton’s Corpuscular Theory

According to Sir Isaac Newton light consists of extremely small spherical perfectly elastic particles called corpuscles which are emanating from a source with tremendous speed and whose impact on the retina causes the sensation of vision. This theory could satisfactorily explain the rectilinear propagation and reflection but the explanation given to refraction of light was found wrong later. Newton said that the particles of a denser medium attracted the corpuscles towards them and causes the light to bend at the interface between the two media. If this were correct, light could travel with a greater speed in a denser medium as it would be accelerated more due to the force of attraction by the particles of the denser medium.  But when the velocity of light in different media was found experimentally, it was observed that the velocity of light is less in a denser medium. Further, Newton’s theory could not explain color vision, interference (color in soap bubble and thin films), diffraction (bending of light at sharp opaque obstacles) etc .

Huygens’ Wave Theory

The wave theory proposed by Christian Huygens in 1678 could explain all the above phenomena satisfactorily but failed to explain photoelectric effect (the emission of electrons from the surface of alkali metals when light is incident on it).  Further, Huygens considered light as a longitudinal waves, but the phenomenon of polarization suggests that light is transverse in nature.

Electromagnetic Wave Theory

James Clark Maxwell established the Electromagnetic wave theory in 1864 and he calculated the velocity of electromagnetic waves in vacuum to be 3 x 108 m/s which coincided with the value of experimental value of velocity of light in air. This coincidence led the scientists to conclude that light is an electromagnetic wave.

Dual Nature of Light and Quantum Theory

Even the electromagnetic wave theory could not explain photoelectric effect (for which the particle nature of light is to be used where a ‘light particle’ strikes off an electron from a metal surface). So we have to consider that light has a dual nature; ie, it is a particle as well as a wave at the same time.

According to Max Plank’s Quantum Theory, light is an electromagnetic form of energy emitted as packets called quanta (quantum is the singular form) or photons. The photons possess dual nature.


Electromagnetic Waves is the smallest chapter for Class XII students and CBSE has assigned 3 marks for this chapter.

You can download the lecture notes from Electromagnetic Waves here

Wednesday, October 6, 2010

How to Score high Grades in CCE?

CBSE has renovated the evaluation system and classes VI to X is now following the Continuous and Comprehensive Evaluation (CCE).

Here are some tips and guidelines to help you score better grades in CCE.

The most important step in scoring high grades in CCE is to:

“Let the teachers know you well”

Grades are awarded to students based on work experience skills, dexterity, innovation, steadiness, teamwork, public speaking, behaviour, etc. to evaluate and present an overall measure of the student's ability. This helps the students who are not good in academics to show their talent in other fields such as arts, humanities, sports, music, athletics, etc.

  • Consider your teacher as your elder brother and discuss your doubts and problems with your teacher. This will help the teacher in knowing your personality well so that he/she become aware of your strengths and will be able to help you overcome your weaknesses.
  • Show initiative in classroom activities.image
  • Obey the orders and requests by teachers politely and try to be as perfect in your work as possible.
  • Express your ideas. If you have an innovative idea, share it with your teachers.
  • Always respect your teachers and greet him / her with a smile and sincerity.
  • Make sure that your teachers know you by name and by face. This can be realized by introducing yourself to your teacher whenever you happen to interact with him/her. Interact with your teacher whenever possible. (May be direct, over phone or on chat). Take care not to annoy him. Your interactions must be on genuine grounds and make short and sweet and to the point.
  • Share your achievements and occasions of happiness with your teacher(s).
  • Maintain a high degree of discipline and persuade your friends also to do so.
  • Be an integral  part of the group whenever you are assigned a group task. Work for the success of the group.
  • Perform your experimental / practical lessons with zeal and confirm that your teacher is impressed with your work.


imageFollow these guidelines and I am sure that you will be getting good grades for your CCE. The most important part of all is to help the teacher identify the real you and recognize your abilities and strengths.

Wish You All the Best

Tuesday, October 5, 2010

ICSE Physics Sample Paper 2011

Click the link below to download ICSE Physics Sample Paper

ICSE Physics 2011 sample paper

ISC Physics Sample Question Paper

Click ISC_SPECIMEN_QP_2011_pp22-30 to download Physics Sample Paper for ISC 2011

The Bare Minimum Package for Class XII - Alternating Current

Find below a collection of chosen questions and answers for those who find it difficult to get good marks in Physics. Please download and study the answers well. We plan to provide such packages for all chapters.

Please provide your comments so that we can improve this initiative as per your need.

Click class_xii_ac_circuits to Download Study Materials for Alternating Current

Monday, October 4, 2010

CBSE Class X Physics SA 1 Questions and Answers

        1. Suggest two reasons which make the large scale usage of nuclear energy prohibitive.
        2. Why are solar cookers  covered by a glass plate?
        3. What is the colour of insulation over the earth wire? Why is an earth wire connected to metallic part of appliances?
        4. What are the factors on which the resistance of a conductor  depends upon? Write a mathematical expression for the same.
        5. What is a solar panel? Mention any three of its applications.
        6. Write four characteristics of a good source of energy.
        7. Why is a series arrangement not used in domestic circuits?
        8. An electric iron has rating 750 W, 220 V; Calculate (i) Current passing through it, (ii) Its resistance when in use.
        9. Draw magnetic field lines around a bar magnet. List any two properties of the magnetic field lines.
        10. How can a piece of soft iron be transformed into an electromagnet? Draw a circuit diegram to show the same.
        11. (a) A 12 V battery is connected to the arrangement of resistors below. Calculate (i) the total effective resistance of the arrangement. (ii) The total current in the following circuit.

(b) State Ohm’s law. What constant can be obtained by calculating the slope of a VI graph?