Home » 2010 » December

Monthly Archives: December 2010

What is the principle used in the working of 3D glasses?

Sreeda asked:

What is the principle used in the working of 3D glasses?


3D glasses are actually polaroids. They are not creating the 3D effects. The 3 D movies are filmatographed with two cameras help at two different angles just like we see with TWO eyes.

The two films are projected on the screen with polarized light with their plane of polarization in perpendicular to each other. If we look at the screen without ant 3D glass we will see blurred images only as the two pictures are overlapping each other and both the image are seen together by both the eyes.

3D glasses use Polaroid with the plane of polarization in mutually perpendicular directions. So, when we wear the Polaroid glasses and look at the screen, only one of the image will be seen by one of the eyes and the second eye sees the other image. This creates the 3D sensation, we are seeing the image filmed with the left camera with the left aye and that with the right camera with right eye.

MAGNETISM : Why repulsion is told to be the test for magnetism?

Sreeda sked:

“Can a magnet lose its magnetic properties?How?
Why ‘repulsion’ and not ‘attraction’  is suggested to be a good test of finding whether a substance is a magnet or not?”


A magnet can lose its magnetism.

A magnetic substance is made a magnet by making the molecules which are individually possessing magnetic properties align in a particular direction. In the unmagnetized state they are arranged randomly and hence do not have magnetic behaviour.

If a magnet is heated, beaten, mishandled etc, it will lose its magnetism.

Why repulsion is the sure test for magnetism?

A magnet can attract the opposite pole of other magnet as well as the magnetic substance (iron cobalt nickel). SO, if A magnet attracts another object, we cannot say that the other object is a magnet. But if the magnet repels the object, then we can surely say that the other object is a magnet. Because “Like poles of a magnet repel each other”


“Sir, is it true that in magnetic hill in Ladhak defies gravity? If so, Why?”
The “magnetic hill” is located on the Leh-Kargil-Batalik national highway, about 30 km from Leh, at a height of 14,000 feet above sea level. On its eastern side, flows the Indus, which originates in Tibet and goes to Pakistan. The Indian Army maintains a sikh Gurudwara near the hill where Guru Nanak Dev, meditated in the 17th century.[citation needed] Due to both the Gurudwara and the gravity hill, the area has become a popular sightseeing destination.
The hill is alleged to have magnetic properties strong enough to pull cars uphill and force passing aircraft to increase their altitude in order to escape magnetic interference; in reality, the effect is an optical illusion created by the gravity hill.
The slope of gravity hills is an optical illusion, although sites are often accompanied by claims that magnetic or even supernatural forces are at work.
The most important factor contributing to the illusion is a completely or mostly obstructed horizon; without a horizon, judging the slope of a surface is difficult as a reliable reference is missing. Objects one would normally assume to be more-or-less perpendicular to the ground (such as trees) may actually be leaning, offsetting the visual reference. The illusion is similar to the well-known Ames room, in which balls can also appear to roll against gravity.

Physics and Mobile Phones

Sajin John asked:

“Where is physics in mobile other than circuits?”


A mobile phone uses Physics throughout its functioning as well as the communication techniques involved.”

Follow these links for more information.



Life Live and Waves

Sreeda Asked:

Is lifeline actually a wave?


First of I have to clarify the question.

The word LifeLine has got more than one meaning.

See the link below for various reference to LifeLine


I hope your reference is towards ECG (If not, please respond to this post through the commenting system)

“The ECG works mostly by detecting and amplifying the tiny electrical changes on the skin that are caused when the heart muscle “depolarises” during each heart beat. At rest, each heart muscle cell has a charge across its outer wall, or cell membrane. Reducing this charge towards zero is called de-polarization, which activates the mechanisms in the cell that cause it to contract. During each heartbeat a healthy heart will have an orderly progression of a wave of depolarisation that is triggered by the cells in the sinoatrial node, spreads out through the atrium, passes through “intrinsic conduction pathways” and then spreads all over the ventricles. This is detected as tiny rises and falls in the voltage between two electrodes placed either side of the heart which is displayed as a wavy line either on a screen or on paper. This display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.” (Wikipedia)

The following links will be of help to learn more about ECG, its working and a little history





A wave is the mechanism of transfer of energy through vibrations. In an ECG a waveform is generated corresponding to the pulses produced by heartbeats.

As such ECG cannot be treated as a wave. But the term wave is used to talk about the screen or print pattern obtained because of the graphical similarity with a wave pattern.

(Click the image on left for an animation of heart beats and the corresponding ECG obtained)

(I don’t think this as a complete answer. Anyone with better knowledge can add to this through comments)

DOWNLOAD the ebook  “How ECG works” here

Mass Energy conversion and the Big Bang

Ajesh Asked:

Respected sir, in the famous theory of Albert Einstein which is of mass energy equivalence  he stated a formula E = mc2 .
sir does this mean that mass can be converted in to energy or the opposite will happen .
it is even stated in the big bang theory  that the universe was created with respect to the  above theory is that so?



The mass energy conversion and the equivalence is a widely discussed topic in relation to the creation of the universe or the Big Bang.

There is some energy missing in calculation when we consider the equivalence; this is called dark energy.

Please read the following links for more details.




Ask Physics Forum

As per request from students, I have created a forum where students can register login and post their questions. Any member can ask questions or post answer to the questions posted. This is on trial basis. If found not secure against spam or illegal activities, the site will be stopped.

Visit the ask physics forum here

Hits so far @ AskPhysics

  • 2,274,296 hits

You may also be interested in

Subscribe to AskPhysics via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Join 4,341 other subscribers

December 2010

Learn Self Defence Techniques online

%d bloggers like this: