What is Quantum Mechanics ?

Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic scales.

Wormhole

Deepa asked:

“What is a worm hole?”

Ans:

A wormhole is a hypothetical topological feature of spacetime that would be, fundamentally, a "shortcut" through spacetime.

A wormhole is, in theory, much like a tunnel with two ends each in separate points in spacetime.

There is no observational evidence for wormholes, but on a theoretical level there are valid solutions to the equations of the theory of general relativity which contain wormholes. The first type of wormhole solution discovered was the Schwarzschild wormhole which would be present in the Schwarzschild metric  describing an eternal black hole, but it was found that this type of wormhole would collapse too quickly for anything to cross from one end to the other. Wormholes which could actually be crossed, known as traversable wormholes, would only be possible if exotic matter with negative energy density could be used to stabilize them

Faster than light Travel
Wormholes allow superluminal (faster-than-light) travel by ensuring that the speed of light is not exceeded locally at any time. While traveling through a wormhole, subluminal (slower-than-light) speeds are used. If two points are connected by a wormhole, the time taken to traverse it would be less than the time it would take a light beam to make the journey if it took a path through the space outside the wormhole. However, a light beam traveling through the wormhole would always beat the traveler. As an analogy, running around to the opposite side of a mountain at maximum speed may take longer than walking through a tunnel crossing it.

Ref: Wikipedia

Indian Journal of Pure & Applied Physics (IJPAP) Browse the Latest articles published

List of Articles:

EPR study of free radicals in amino acid derivatives gamma-irradiated at 300 K
Aydin, Murat
611-614
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FTIR study of modification of transition metal on zeolites for adsorption
Bardakçi, Belgin; Bahçeli, Semiha
615-620
View Full Text

Total ionization cross-sections of atmospheric molecules due to electron impact
Kumar, Yogesh; Tiwari, Neelam; Kumar, Manoj; Tomar, Surekha
621-625
View Full Text

Spectral editing with 2D E-HMQC NMR spectroscopy for CD_n groups: A theoretical study
Şaka, İ; Gümüş, S; Gençten, A
626-631
View Full Text

Characterization of iron slag of Kakching, Manipur by X-ray and optical spectroscopy
Sheikh, M R; Acharya, B S; Gartia, R K
632-634
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Automatic optical inspection system for the image quality of microlens array
Lin, Chern-Sheng; Ho, Chen-Wei; Yang, Shih-Wei; Chen, Der-Chin; Yeh, Mau-Shiun
635-643
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Acoustical properties of ternary mixtures of 1-alkanols in di-isopropyl ether and 2,2,2-trifluoroethanol mixed solvent
Palani, R; Balakrishnan, S
644-650
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Acoustic and viscosity studies of alkali metals and ammonium halides in aqueous dextran solutions at four different temperatures
Dash, U N; Roy, G S; Talukdar, M; Moharatha, D
651-657
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Structural, thermal and optical properties of Cu²⁺ and Co²⁺: PVP polymer films
Sivaiah, K; Rudramadevi, B Hemalatha; Buddhudu, S
658-662
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Effect of pressure and temperature on C₆₀ fullerite
Sharma, Uma D; Joshi, H; Kumar, M
663-667
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Microwave dielectric relaxation, thermodynamic and conformational studies of hydrogen bonded binary mixtures of propan-1-ol with methyl benzoate and ethyl benzoate
Mohan, T Madhu; Sastry, S Sreehari; Murthy, V R K
668-675
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Use of modern telephone network for time transfer: An innovation
Thorat, Pranalee P; Banerjee, P
676-680
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Recent Articles

Use of modern telephone network for time transfer: An innovation

Microwave dielectric relaxation, thermodynamic and conformational studies of hydrogen bonded binary mixtures of propan-1-ol with methyl benzoate and ethyl benzoate

Effect of pressure and temperature on C₆₀ fullerite

Structural, thermal and optical properties of Cu²⁺ and Co²⁺: PVP polymer films

Acoustic and viscosity studies of alkali metals and ammonium halides in aqueous dextran solutions at four different temperatures

Question from Wave Optics

Rajat Asked:

What is the difference between interference and diffraction?

Ans:

Interference is caused by the superposition of wave fronts from two coherent sources; But diffraction is caused by the superposition of wavelets from a single wavefront when it confronts an obstacle or a slit.

Note: Visitors are requested to add to the answer through comments

Question from Beats (Waves)

Sanjeet asked:

"the displacement of a particle in periodic motion is given by "y=(cos2t-2cost+2sin^2t+1). What is the no. of beats that can be heard in 10 seconds?"

Question from Rotational Dynamics

Dyana Asked:

A small rubber wheel is used to drive a large pottery wheel. The two wheels are mounted so that their circular edges touch. The small wheel has a radius of 3.5 cm and accelerates at the rate of 7.9 rad/s^2, and it is in contact with the pottery wheel (radius 23.0 cm) without slipping.
a)Calculate the angular acceleration of the pottery wheel
b)Calculate the time it takes the pottery wheel to reach its required speed  of  64 rpm

Students and teacher visitors are requested to respond

Research Links

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http://nopr.niscair.res.in/handle/123456789/10052

Amateur Research

Ask Physics is looking for students from Kendriya Vidyalayas of Kerala who are interested in doing Research in any branch of Science.

If interested, Use the link below to express your interest.

You will be contacted by the concerned official.

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Van de Graff Generator Pics

Electric Flux

From: Nancy James

Subject: Electric flux
Message Body:
Could some one please explain what is written in the ncert book of PHYSICs class XII about 'electric flux'?

Save the images, open and zoomin to read

A Question from Current Electricity

Pratham asked:

The resistances of 2 bulbs are in the ratio 1:2.if they are joined in series,find the ratio of the energy consumed by the 2 bulbs?

 

Answer:

When connected in series, the same current flows through each of the resistors. Therefore, the energy dissipated is directly proportional to their resistances. That is, the ratio of energy dissipated will nbe same as the ratio of resistances. (1:2)

Doubt from HC Verma’s Concepts of Physics Volume I

If any one can explain step wise calculation of Example no. 17 of Chapter 2 of concepts of Physics by H C Verma Vol. 1.
Thanks in advance

Ans:



Solutions to the entire problems from concepts of Physics by HC Verma available at http://sites.google.com/site/physicsclassroomonline as well as www.plustwophysics.com

Prof. At IISER Has Been Appointed As India's Research Ambassador

Deutscher Akademischer Austausch Dienst (DAAD), popularly known as German Academic Exchange Service, has appointed Prof. A.A. Natu, IISER, as India’s research ambassador at a function held in New Delhi on August 19, 2010. Mr. Christiane Schlotmann, Head DAAD, New Delhi, conferred the honor on him for his exemplary dedication, leadership and commitment in encouraging Indo-German relations in the area of education and research. "DAAD promotes Indo-German co-operation in the area of education and research awarding scholarships at graduate, post graduate and doctoral level for studies in Germany. It has recently introduced a programme called working internships in science and engineering,' wherein undergraduate students from 63 institutes across India can get scholarships for three months for practical training to carry out research projects," said Prof. A.A. Natu.

What are Mesons?

In particle physics, mesons are subatomic particles composed of one quark and one antiquark. They are part of the hadron particle family—particles made of quarks. The other members of the hadron family are the baryons—subatomic particles composed of three quarks.

The main difference between mesons and baryons is that mesons are bosons while baryons are fermions—that is, mesons have integer spin while baryons have half-integer spin—meaning that the Pauli exclusion principle does not apply to mesons.

 

Each meson has a corresponding antiparticle (antimeson) where quarks are replaced by their corresponding antiquarks and vice-versa.

A change in view point !

Mirage

Numericals from Kinematics

PHYSICS TEST (CLASS XI) Kinematics

1. A particle is projected at 60º to the horizontal with a kinetic energy K. What is the kinetic energy at the highest point


2. Which of the following statements is false for a particle moving in a circle with a constant angular speed?
   (a) the velocity vector is tangent to the circle
   (b) the acceleration vector is tangent to the circle
   (c) the acceleration vector points to the centre of the circle
   (d) the velocity and acceleration vectors are perpendicular to each other


3. A car is moving in a circular horizontal track of radius 10.0 m with a constant speed of 10.0m/s.A plumb bomb is suspended from the roof of the car by a light rigid rod of length1.00m. What is the angle made by the rod with the track is (g= 10 m/s²)


4. The distance traveled by an object along the axes are given by x=2t², y = t² - 4, z = 3 t - 5. What is the initial velocity of the particle


5. A boy playing o the roof of 10m high building throws a ball with a speed of 10 m/s at an angle of 30º the horizontal. How far from the throwing point will the ball be at the height of 10m from the ground?


6. If a body travels half of its path in the last second of its fall from rest; find the time and height of its fall?


7. An object A is kept fixed at the point x = 3m and y=1.25m on a moving along the +x direction with an acceleration 1.5 m/s. At the same instant a stone hitting the object during its downward motion at an angle pf 45º to the horizontal .all the motions are in X-Y plane .Find u and time after which stone hits the object. Take g = 10m/s²


8. Three particles a, b and c are situated at the vertices of an equilateral triangle ABC of side d at t=0. Each of the particles moves with constant speed v. A always has its velocity along BC and C along CA. At what time will the particles meet each other?


9. A man standing on road has to hold his umbrella at 30º with the vertical to keep the rain away he throws the umbrella and starts running at 10 km/h. he finds that  raindrops with respect to [a]the road, [b] the moving man.

10. A man can swim at speed of 3 km/h in still water. He wants to cross a 500 m wide river flowing at 2 km/h. he keeps himself always at an angle of 120º with the river flow while swimming. (a) Find the time he takes to cross river. (b) At what point on the opposite bank will he arrive?

11. A staircase contains three steps each 10cm high and 20 cm wide what should be the minimum horizontal velocity of a ball rolling off  the uppermost plane so as to hit directly the lowest plane?

12. A person is standing on a truck moving with a constant velocity of 14.7 m/s on a horizontal road .The man throws a ball in such a way that it returns to the truck after the truck has moved 58.8 m .find speed and the angle of projections
(a) as seen from the truck, (b) as seen from the road

13. An airplane has to go from a point A to another point B, 500 km away due 30º east of
north. a wind is blowing due north at a speed of 20 m/s (a) find the direction in which the pilot should head the plane to reach the time taken by the plane to go from A to B

www.plustwophysics.com

What is impact parameter?

Impact parameter is the perpendicular distance between the velocity vectors of two objects (considered to take part in a collision) when they are at infinite distance (at such a distance that there is no interaction between the two particles)

In Rutherford’s alpha scattering experiment, the gold nucleus is at rest and therefore, in this case

Impact parameter is the perpendicular distance between the gold nucleus and the the direction of the velocity vector of alpha particle when the alpha particle is at infinite distance (i.e; the force of interaction between the gold nucleus and the alpha particle is negligibly small)

Why ordinary ammeter cannot measure AC?

Ac changes its direction frequently and therefore the ordinary ammeter which is just a galvanometer with a shunt, tends to respond to the magnitude and direction of the instantaneous values of current and in effect it will not show any deflection.
Ac is measured using hot wire ammeter, which is based on the heating effect of current

A question from maths

There are six points in a plane. The largest distence between two points is D and smallest distence is d. Find the ratio D/d.

A Question based on Gauss Law

A circular ring of radius r made of a nonconducting material is placed with its axis is parallel to a uniform electric field if the ring rotated by 180 degrees Does the flux changes? A Q charge is uniformly distributed on a thin spherical shell If a point charge is brought near it what is the field at the center?Is u r answer depends on whether it is conducting or nonconducting?

APPLY NOW for KVPY 2010 Fellowships

The "Kishore Vaigyanik Protsahan Yojana" is an ongoing program started by the Department of Science and Technology, Government of India, to encourage students of Basic Sciences, Engineering and Medicine to take up research careers in these areas. The aim of the program is to identify and encourage talented students with aptitude for research.

This program strives to assist the students to realise their potential and to ensure that the best scientific talent is tapped for research and development in the country. Generous scholarships will be provided (up to the pre-Ph.D. level) to the selected students.

click here for more details

GENIUS MEET 2010 -Eduworld

Thiruvananthapuram (14 August 2010)

Eduworld Foundation – A non profit organization aimed at nurturing scientific spirit in children organized Genius Meet 2010 for the students of Trivandrum schools who scored high in class 10 during the year 2010. About 150 students along with their parents participated.

Former chairman of the Indian Space Research Organisation, G. Madhavan Nair interacted with the students.

The participants also got chance to hear and interact with Sh. B.N. Suresh, Director of the Indian Institute of Space Science and Technology; Dr. E.D. Jemmis, Director of the Indian Institute of Science Education and Research; A. Sivathanu Pillai, Chief Executive Officer of BrahMos Aerospace.

Dr. Sivathanu Pillai’s address and presentation were very much appreciated by the audience. All were wonderstruck with the advancement and the high degree of precision India has achieved in the field of missile technology.

The students were taken to a visit to the Science and Technology museum and in the mean time Prof E D Jemmis interacted with the parents of the genius students and stressed on giving freedom for the students to think and choose the right career which they find themselves suitable for. He stressed on the importance of attending the exams like KVPY (Kishore Vygyanik Protsahan Yojana – A scheme introduced by the Govt of India to identify the genius and to grant them scholarship to study in Top Schools and courses like IIT, IIST,IISER etc Get the details here http://www.iisc.ernet.in/kvpy/). He stressed that there is a high need of students selecting research as a career. Pure science is also leading to great jobs with long lasting and healthy work environment than the get rich quick type jobs as in the IT field.

Dr. S.K. Satheesh of the Indian Institute of Science, Bangalore, who won the Bhatnagar Award for 2010, was felicitated at the meet.

 

The Genius Meet 2010 ended with felicitation of the top scoring students and the National Anthem

The eyes of the students were sparkling with inspiration and motivation while they came out of the meet.

GENIUS MEET 2010 -Eduworld

Thiruvananthapuram (14 August 2010)

Eduworld Foundation – A non profit organization aimed at nurturing scientific spirit in children organized Genius Meet 2010 for the students of Trivandrum schools who scored high in class 10 during the year 2010. About 150 students along with their parents participated.

Former chairman of the Indian Space Research Organisation, G. Madhavan Nair interacted with the students.

The participants also got chance to hear and interact with Sh. B.N. Suresh, Director of the Indian Institute of Space Science and Technology; Dr. E.D. Jemmis, Director of the Indian Institute of Science Education and Research; A. Sivathanu Pillai, Chief Executive Officer of BrahMos Aerospace.

Dr. Sivathanu Pillai’s address and presentation were very much appreciated by the audience. All were wonderstruck with the advancement and the high degree of precision India has achieved in the field of missile technology.

The students were taken to a visit to the Science and Technology museum and in the mean time Prof E D Jemmis interacted with the parents of the genius students and stressed on giving freedom for the students to think and choose the right career which they find themselves suitable for. He stressed on the importance of attending the exams like KVPY (Kishore Vygyanik Protsahan Yojana – A scheme introduced by the Govt of India to identify the genius and to grant them scholarship to study in Top Schools and courses like IIT, IIST,IISER etc Get the details here http://www.iisc.ernet.in/kvpy/). He stressed that there is a high need of students selecting research as a career. Pure science is also leading to great jobs with long lasting and healthy work environment than the get rich quick type jobs as in the IT field.

Dr. S.K. Satheesh of the Indian Institute of Science, Bangalore, who won the Bhatnagar Award for 2010, was felicitated at the meet.

 

The Genius Meet 2010 ended with felicitation of the top scoring students and the National Anthem

The eyes of the students were sparkling with inspiration and motivation while they came out of the meet.

Devices using permanent magnets and electromagnets

Galvin Pinto asked;

1. List the devices where permanent magnets & electromagnets are used.
2. Sketch the pattern of the field lines around a current carrying:

• Straight Conductor

• Loop of wire

• Solenoid

Ans:

1. Permanent Magnets are used in
• Laboratory magnets
• loud speakers
• microphones
• cyclotron
• generators
• and many more
2. Pattern of the field lines around a current carrying

Straight Conductor

Loop of wire

Solenoid

A Question from Magnetic Effects of Current

Gavin Pinto asked

“A current carrying wire is placed above a magnetic needle. What do you observe? If you want to increase this effect, what will you do? If you want to reverse the effect, what will you do?”

 

Ans: When a current carrying conductor is placed above a magnetic needle, the magnetic needle is deflected and tends to align itself perpendicular to the conductor. The effect can be increased by increasing the strength of current through the wire or by decreasing the distance.

However, the maximum deflection which can be produced is 90 degree, when the magnetic field produced by the current carrying wire is very much greater than the earth’s magnetic field.

A question for you from electronics !

Which of the following two circuits will give rectified output for the both the half cycles of a.c. input?

Links to help you understand the production of electromagnetic oscillations in LC circuit

Capacitors and inductors are capable of storing energy in the electric field and magnetic field respectively.

No A.C elements i.e., capacitor, inductor are pure. In other words each of them do have some resistance. The charges or current through these elements lose their energy as heat due to the resistance. The energy is radiated away in form of electromagnetic wave, which is the basis of radio, T.V transmission. As the circuits give away this energy, this loss has to be replenished. This is done using a L.C circuit. Consider the circuit below:

The capacitor, which charged, is connected to the indicator. The capacitor starts discharging i.e., the charges on capacitor start decreasing. If q and I were the charge and current then according to Kirchoff's Law.

(i.e., e.m.f across C = e.m.f across L)

The solution for the above equation being

i.e, the charge and hence current is oscillatory. This means its magnitude and direction keeps changing. The charge on the capacitors going through the inductor generates a magnetic field and thereby some energy is stored in the magnetic field. The current slowly reaches a maximum when the capacitor is fully discharged. The induced current in the inductor opposes this and charges the capacitor in opposite direction.

The whole process repeats once again. The energy of system oscillates between capacitor and the inductor.

http://wiki.4hv.org/index.php/LC_Oscillator

http://en.wikipedia.org/wiki/LC_circuit

http://www.phys.unsw.edu.au/~jw/LCresonance.html

A Random Test from Magnetism

Each question carries one mark

• What is a magnetic dipole?
• What is the difference between electric field lines and magnetic field lines?
• Write an expression for the magnetic field at a point on the axis of a circular group carrying current and hence write equation for the magnetic dipole moment of the loop?
• What is Bohr magneton and write its equation and value?
• State Gauss’s law in magnetism?
• Define magnetic meridian?
• Define magnetic declination?
• Define angle of dip or magnetic inclination?
• Define magnetizing force and intensity of magnetization?
• Draw the hysteresis loop for a ferromagnetic substance.
• Define retentivity and coercivity
• Repulsion the surest test of polarity. Comment
• State Curie’s law of magnetism
• Define magnetic susceptibility
• Compare the relative permeability of paramagnetic , diamagnetic and ferromagnetic substances.

Gauss`s law

Nagendra chowdary asked : -

“A circular ring of radius r made of a non conducting material is placed with its axis is parallel to a uniform electric field if the ring rotated by 180 degrees Does the flux changes? A Q charge is uniformly distributed on a thin spherical shell If a point charge is brought near it what is the field at the center?Is u r answer depends on whether it is conducting or non conducting?”

Optics

Rajat asked:

“when we exchange the lenses of compound microscope, then why it does not act as a telescope?”

Questions from Properties of gases

Senarita asked:

“we know that temperature has a properties to make some thing bigger in volume.we say that gas has no particular volume or shape.where we place a gas it takes the shape of that container.my question is- a gas of mass 'm' has a particular number of atoms or molecules.if the gas is not getting any temperature then how it is occupying all the volume of a bigger container.i mean how the inner space of two atoms or two molecules of that particular gas is increasing when i am transferring it to a bigger container.(say,every condition is constant.nothing is changed.)please answer me.”

“can you give me some name of sites where i can get explanations on hydrostatics or the topics of physics.i am now in class 11.”

Master will be answering the question shortly. The visitors are requested to respond

A Question from Electromagnetic Waves

Rajat asked: -

we know that electric and magnetic field are associated with charged particle but when light travells,it produces electric and magnetic field both but it consests of photons,which is a uncharged particle.why it did so?



Master will soon answer this.

By the time, if any visitor wants to answer, please use the commenting system

Motion in a circular path

aashish davis asked:

“A man moving on a circular triangle of radius 100 m. completes 1 revolution in 4 min. what is his average speed? average velocity in full revolution?”

Average speed = total distance / total time = 2πr/(4x60)= 2.61 m/s

Average velocity = zero since the displacement =0 in full revolution

An Idea on UltraSonics

Sarin John Skaria Asked:

“We know that a kidney stone is broken down by using ultrasound waves.now think about creating a machine which can produce a large no.of ultrasound waves in an instance . it will be useful for us to create a tunnel under a hill,for digging a hole in the ground rapidly.”

Law of mass action

When an intrinsic semiconductor is doped with pentavalent impurity, the number of free lectrons increases. Will it result in any change in the number of holes already present?

The answer is YES.

When the semiconductor is doped with pentavalent impurity, the n_e increases and will result in a decrease in n_h according to the relation.

n_i² = n_in_h

This relationship is called the mass action law.

When the no. of free electrons increases, greater no. of holes already present get neutralised.

The difference between electricity and electronics

Electricity is the branch of Physics (?) which deals with the flow of electrons and its effect. The electric bulb, electric iron etc are electric devices as they are based on the direct effects like heating effect of current.

Electronics is the branch of Physics (?) which deals with the control of the flow of electrons (by allowing or disallowing or regulating the percentage of flow) through a device.

The television, calculator, computer are all electronic devices. Evidently they are not limited to the direct effect of flow of electrons through a conductor or a resistor ar any other transducer.

Now, try to classify the following appliances into electric devices and electronic devices.

1. transistor radio


2. sodium vapour lamp


3. ups


4. television


5. electromagnet


6. geyser


7. calling bell


8. voting machine


9. soldering iron


10. quartz clock


11. desoldering machine


12. electric iron

Nowadays, many electric appliances are also fitted with some electronic component. Can you site some examples?

Doping

Doping is the deliberate addition of desirable impurities to an intrinsic semicounductor to modify its conducting propertires.

The impurity atoms added are called dopants and the semi conductor so formed is called extrinsic semiconductor.

Depending on the type of impurities added, extrinsic semiconduictors are divided into two : n -type and p-type.

Note:

The extrememly pure form of semiconductor is called intrinsic semiconductor.

The conductivity of an intrinsic semiconductor is extremely low (but greater than insulators), and therefore as such there is no much practical use of intrinsic semiconductor. But when suitably doped to make extrinsic semiconductor, it works wonders. We get greater control over the flow of electrons.

Launching Soon !! ThinkJunction.com ThinkJunction.org ThinkJunction.net ThinkJunction.info

ThinkJunction : A new website is about to launch.

What do you expect at ThinkJunction?

Post your expectations as comments.

New Policy For Engineering Program This Year

In this academic year, students will find some new changes in the admission process of engineering colleges in Gujarat. Until now, students had been following the upgradation structure but from this year, they will have to follow a reallocation policy. As per the new policy, a candidate who has taken admission in a particular branch but now wants to opt for another branch would need to submit his/her previous seat to get an admission in the desired engineering branch. Mr. MN Patel, Principal of LD Engineering College and head of the admission committee, said, “It is not going to affect the career of the students much. The only difference is that first they had the option of holding on to their earlier branch, but now they will get a chance to reshuffle depending on the availability of the college and the branch that they have requested for.”

Source : dnaindia.com

Electricity – Class X CBSE

Some important points to remember

• The resistance of a conductor does not change when the current through it is changed or the voltage across it is changed. When current is changed, the voltage across it is also changed so that the ratio V/I = R
• The value of resistance changes if the dimensions (length or area of cross section of the conductor) changes or the temperature changes.
• When the dimensions of a conductor is changed, the resistance changes, but the resistivity does not change.
• When temperature is changed, both resistivity as well as resistance changes.

Electric Fuse – A Safety Device

 

• Electric Fuse is a Safety device
• It works on the principle of Joule’s law of heating
• It consists of a fuse wire made of an alloy of tin and lead, which melts and breaks the circuit whenever current in the circuit exceeds safe limits due to overloading or short circuit