# Search results

1. ### I Interpreting "momentum" in WKB approximation

According to WKB approximation, the wave function \psi (x) \propto \frac{1}{\sqrt{p(x)}} This implies that the probability of finding a particle in between x and x+dx is inversely proportional to the momentum of the particle in the given potential. According to the book, R. Shankar, this is...
2. ### GRE with 3 years of Bachelors degree?

Hi, I am currently in my 3rd and final year of B.Sc Physics. Soon I'll have to start applying for a Masters degree. Is it true that you need 4 years of bachelor degree to get admitted for Postgraduate via GRE exam? If so, is there any university outside India which will accept my 3 year course...
3. ### Clarification about stationary quantum states of a system

Okay, here goes... Our teacher set a question in the last test which asked us to show that if a system initially be in a stationary state, it will remain in a stationary state even if the system evolves according to the time dependent Schrodinger equation. What I did was show that the...
4. ### Gauss' Law in a dielectric material

This is what we have in text-books and in Wikipedia: ρ=ρb+ρf and from there we get ∇.D=ρf. But I am unable to understand why we are not considering the bound surface charge in deriving this equation. Can anyone explain this to me.
5. ### Is the Moment of Inertia strictly different

I would like to know if there is any proof as to whether the moment of inertia for two bodies (the masses of each body are distributed on a line) about their respective center of masses, is strictly different. If not, can anyone provide me a link to where the work is computed.
6. ### Width of a wire grid polarizer

Why is it that the width of a wire grid polarizer has to be less than the wavelength of the wave which I want to polarize? What would happen if the width was a little bit more?
7. ### Kelvin's thunderstorm generator

I came across this experiment where two flowing streams of water, each falling through a can/inductor and finally falling into a bucket (metallic) creates a huge electrical potential difference! Ok I know that the falling water droplets have to acquire electrical charges, but I just can't figure...
8. ### Where to do my MSc?

Hello everyone, I am a 1st year undergraduate student of physics, in Kolkata,India. I wanted to know what good places are there to do my master's degree from, both in India and abroad, and what scholarships I can get. Thank you.
9. ### Photons being affected by pseudo forces

I was reading a book called "Hyperspace", by Michio Kaku, and there he gave a sort of introduction to general relativity. Well its not at all technical, just for reading and knowing... There he claimed that space is curved because light rays will take a bent path inside an accelerating...
10. ### Car with a balloon

Hi everyone, I was just wondering about this... If I tie a balloon outside a car, using a moderately long string, and the car heads for a left turn on the road with constant speed, then while turning, what would be the path followed by the balloon? I was thinking that maybe the balloon...
11. ### Minimum velocity at bottom of pendulum

Homework Statement A pendulum is made of a rigid rod (mass m, length l) and a small bob of mass M attached at one end. The rod is pivoted on the other end. What should be the minimum speed of the bob at its lowest point so that the pendulum completes a full circle? Homework Equations...
12. ### Getting a patent

What should I do in order to get a recognition for a method I came up with? Should I get a patent? If yes, then how? If no, then what should I do to tell the world that I came up with the method?
13. ### Squaring numbers

Ok, I don't know if this method is already known or not, but I found this all by myself after some observations... so here it is... Suppose we want to square a number, say 67. What i have found is this: 1. First get 652 which is [6*7][5*5] = 4225 2. Forget the digit in the unit's place, ie...
14. ### The circumference of an ellipse

I was wondering about how to find the circumference of an ellipse. I googled for it and found this: http://paulbourke.net/geometry/ellipsecirc/ That got me pretty amazed! I don't know high level maths, but still, can someone please explain to me why the circumference takes such a complicated...
15. ### Acetic acid to propanoic acid

Without using a cyanide
16. ### Work done to pull the entire chain

Homework Statement A chain of mass 4Kg and length 2m is lying on a table, such that 60 cm of one end is hanging from one edge off the table. Find the work done to pull the entire chain on the table. Homework Equations (anything that'll work i suppose) The Attempt at a Solution I...
17. ### Rate of change of angular velocity

Let a particle of mass m be rotating in a circle, radius be r, axis of rotation through the center and perpendicular to the plane of motion. Now if the radius is made decrease somehow at some rate until it get's zero, how do I find the rate of change in angular velocity? Also, the angular...
18. ### Violating the law of conservation of energy

I know that's impossible, so please help me!!! Let there be a body rotating about its axis, with a moment of inertia I and an angular velcity w. The angular momentum of the system is L = Iw. Now, if the radius of the body change, its moment of inertia will also change. Let the new moment of...
19. ### Cinnamaldehyde from cinnamic acid

Can somebody please tell me how to convert cinnamic acid to cinnamaldehyde? I was planning to first make it into the alcohol and then use PCC, but then wondered that reducing the acid might also reduce the α β unsaturated carbons too. Is there any reagent that would do the trick without causing...
20. ### Accelerated charges

My days in high school are almost at an end and I don't want to run to my teachers with this question. So can someone please explain this to me: why an accelerated charge emits photons and loses energy? Links and references are also welcome. Thanks in advance.
21. ### The translational force on a piece of iron in a magnetic field

Ok so if there be a piece of iron in a uniform magnetc field B, what will be the force on the iron? You can assume any variable you want, but i want to find the magnetic force that causes the iron pieces to move towards the magnet in terms of any variables, like it corss-sectional area, length...