Monday, January 31, 2011

Demo Chapters from Vidya Drishti - A site by IITitans for IIT aspirants


  • SHM 1 (PowerPoint presentation; best viewed in office 2007) Click here

  • Coulomb's Law (PowerPoint presentation; best viewed in office 2007 Click here

  • Solved problems of kinematics (PowerPoint presentation; best viewed in office 2007)Click here

  • Solved problem of Newton's Laws (pdf file) Click here

Find more and purchase course materials online at

Friday, January 28, 2011

A problem from light for class X

Sudhanshu Misra posted:
"An object is placed at a distance of 10cm from convex mirror of focal length15cm; find the position and nature of image?"


f= 15 cm

u=-10 cm


substitute the values in the relation

and get the value of v as 6 cm

The image is virtual, erect and diminished

Some sample questions from Physics for SA 2 of CCE class X

  1. List the three phenomenon responsible for the formation of rainbow. (Ans: Refraction, Dispersion, (Total)Internal reflection)

  2. Why do stars twinkle, but planets do not? (Ans: The twinkling is caused by the variation of intensity of light entering our eye from the stars. The starts are far away from us and they are seen in a position different from their actual position caused by atmospheric refraction. The position goes on shifting slightly due to changes in atmospheric conditions, changing the intensity of light received by the eyes. But the planets are relatively closer to us and further they do not emit their own light. The apparent changes in position due to atmospheric refraction is also not considerable. So, planets do not twinkle)

  3. What is meant by power of accommodation of human eye? (The ability of human eye to focus on near by objects as well as far off objects without any time lag is called accomodation and the maximum change in the power of human eye during this process is called power of accomodation; and is equal to 4D)

More questions will be posted soon

Why we can’t see the stars, towards the horizon?

Akshay Verma asks:
"i want to know, why we can’t see the stars, towards the horizon?
but we can see stars towards the zenith?
please answer me, i am gonna ask this to my teacher as well."


Such an observation occurs at twilight. The main culprit here is the comparative greater distance of horizon as compared to zenith.

(Answers from visitors are also welcome. Please post your answers as comments)

Thursday, January 27, 2011

what is the thermal conductivity of a perfect conductor?

Soumya asked:
"What is the thermal conductivity of a perfect conductor?"


Please check the link below for a detailed list of thermal conductivities of different materials.

Every good conductor has some thermal conductivity - low or high. Just like superconductor, thermal conductivity may become infinity for a Thermal Superconductor. Thermal Superconductors may become a reality using CNT (nanotubes)

Wednesday, January 26, 2011

KVS Chennai Region Physics Preboard II Question Paper

Please click the link below to download the Question paper for Class XII (Aissce) Preboard Examination conducted by Kendriya Vidyalaya Sangathan, Chennai Region.

Physics preboard Question Paper KVS Chennai Region

Tuesday, January 25, 2011

A numerical problem from Beats

Nithya asks:

  1. "A source of sound frequency 256Hz is moving rapidly towards a wall with a velocity of 5m/s. How many beats per second will be heard if sound travels at a speed of 330m/s?"

  2. a wire of length 140 cm and mass 0.52×10- kg is stretched by means of a load of 16 kg. Calculate the frequency of the fundamental node?


Interference is in complete agreement to law of conservation of energy

Tilak gurjar posted;
"Interference is in complete agreement to law of conservation of energy. Comment"


If there were no interference, the resultant intensity at a point illuminated by two sources will be

I = I1+I2

Due to interference

This shows that energy is conserved even after interference. There is only a redistribution of energy. There is no loss or gain of energy

Wednesday, January 19, 2011

Study On Net Will Be Possible For All In Next Two Years: Kapil Sibal

According to the Union Human Resource Development Minister Kapil Sibal, the government has planned to lay out fibre obtics connecting every village and city of India to facilitate students opt for education right from their homes in the next two years. All the colleges will be linked to the top universities in the country through Internet. The expenditure for the project has been estimated to be around Rs 1,000 crore. The move will help about 20 crore students who have no access to higher education today

Monday, January 17, 2011

A large field is possible by inserting a soft iron core inside the solenoid. Explain why?

PukNitish asks:

A large field is possible by inserting a soft iron core inside the solenoid. Explain why?


Soft Iron has high magnetic permeability, so all the magnetic field lines prefer to pass through it. Thus the magnetic field inside the solenoid is intensified.

Monday, January 10, 2011

CBSE CLASS X Exam Time Table

Click the Link Below to Download the Examination Time Table for Class X CBSE


Sunday, January 9, 2011