# All Questions

127 views

### Is it pure luck to observe a gravitational wave?

I actually have two questions: Since only a gravitational wave that is strong enough can be detected and the GW passes by the earth at light speed, can I say that we are lucky to detect one this ...
32 views

### Why is Kirchoff's Voltage Rule not satisfied when the circuit is shorted?

For example if I have a simple circuit with a battery and a resistor, and then the resistor is shorted, Kirchoff's Rule is no longer satisfied. Since the current through the resistor is 0, the voltage ...
23 views

### The image of a wall clock is to be obtained on the opposite wall 2m away by the means of a convex lens. What is the minimum focal length required?

I'm in 10th grade and this question came in my physics test. Nobody was able to answer this question correctly except my physics teacher who says that the answer is 2m. My answer is that there should ...
14 views

### Best frequency for Underwater Transmission

What is the best frequency of transmission of under the water for communication with good data rate? I have read that the threshold of hearing underwater is around 170 to 180 db. Can this be useful in ...
30 views

### What does the presence of gravity waves show? [duplicate]

Is the essence of the discovery of gravity waves that we now know that gravity propagates through space at the speed of light and not instantly?
27 views

### Temperature of heat and body

Today I was having a cup of tea. I put it on the table, then held it for a while, then drank some tea, than put the cup on the table, and repeated this cycle several times. I noticed that when I was ...
27 views

### What is the structure of an event horizon for colliding black holes?

I would suspect that two black holes within close vicinity of one another would warp each other's event horizons such that the Schwarzchild's radius would no longer apply. Do the event horizons ...
82 views

### How are the 4 km arms of LIGO measured so accurately?

The arms of the LIGO interferometer are 4 km long. Now, LIGO functions by measuring phase difference between two beams of light comming (as in Michaelson's Interferometer) to a sensitivity of ...
20 views

### Will a charge attract or repel bar magnet?

I read in many answers that magnetic fields are basically electrostatic fields arose due to motion of charges usually. It gave me a question, Let there is a charge of 1C in vicinity, and a bar ...
33 views

### why does the chemical potential vanish for Bose Einstein condensate

the reasoning in a Bose Einstein condensate is to try to account for all the particles in the excited continuum states by tuning the chemical potential. However at a critical temperature $T_c$ the ...
13 views

### If magnetic force (hence torque) does no work, how does a dipole placed in a magnetic field have a potential energy associated with it?

If potential energy equals negative of work done and magnetic force does no work what force does the work?
287 views

21 views

### What are some of the best Physics resources online? [duplicate]

Are there any sites similar to (in terms of function and quality) Paul's Online Math Notes, 17Calculus.com, or PatrickJMT.com, for Physics (besides Khan Academy)? I've googled this, but the sites ...
34 views

### How did he find the “lambda” value in this question?

There is a pdf i found when searching about Lagrangian Multpliers, but i was not able to understand how he derived lambda from two differential equations. If anyone can walk me through it, i would be ...
16 views

### Car wheel's “slip ratio” equation for game

Some of you may know about slip ratio. It is specific ratio that kind of depends on wheel rotation speed, radius etc. and affects friction. Car has the most friction at around 0.05-0.1 slip ratio ...
14 views

### IB Physics Internal Assessment [on hold]

What can be good topics for physics internal assessment that can be done in lab especially in electricity or waves portion?
18 views

### How do I start studying astrophysics and it's relations with relativity?

I am a high school student who's very interested in astrophysics and the whole idea that space time is infact a fabric rather than nothing. Unfortunately, my school teaches no where near to any of ...
33 views

### In a $\phi^4$ theory, does the single vertex Feynman diagram (with no internal propagators) contribute to the scattering amplitudes?

If I have an interaction term in the Lagrangian of the form: $$L_{int}=g\frac{1}{4}\phi^4 + g'\phi^3\chi +...$$ How does the trivial diagram (i.e. just a cross with a vertex at the center) ...
16 views

### Cepheid light curves

I've got the light curve of a Cepheid variable. How can I derive (mathematically, not by eye) its period and its average apparent magnitude? i.e., in what form should the best fit curve be? I've read ...
18 views

### Why are fringes displaced when a thin film is introduced (Michelson interferometer)?

I'm reading everywhere that when you place a thin film in one arm of an interferometer, fringes are displaced. No-one seems to explicitly say why; maybe because it's meant to be obvious. I know ...
73 views

### Can Newton's law of gravitation and Einstein's GR be considered true and complete laws of gravitation? [on hold]

Newton's law of gravitation and Einstein's general relativity (GR) are empirical laws of gravitation that are strong on description and prediction but lack deterministic and/or causal rigor, which ...
10 views

### Period-Luminosity relationship in Cepheid variables

I'm investigating the period-luminosity relationship in Cepheid variables. I know such a relationship has already been discovered; however, I'm trying to figure it out by myself as part of a school ...
29 views

22 views

### Is there a way to move a black hole?

Is it possible to move or transport a black hole? What about a white hole?
42 views

### Gravitational waves in other dimensions

I know this question is purely speculative, as we don't know if more dimensions do exist and also we do not know if gravity is indeed stronger in other dimensions (if they were to exist). But, one of ...
29 views

### Gravitational imaging

As the most recent discovery in physics suggested the gravitational waves are now scientific fact. My question is: If that's the case so is it possible in principle to make perfect 3d imaging of an ...
25 views

### Can electron capture occur with an external electron?

Can electron capture proceed with an electron not bound to the nucleus which decays (that is one that is bound to a neighboring atom, bound in a collective state like a conduction band, or free)?
13 views

### Will the Polarity of magnet be reversed or will it rotate? Will the ferromagnet melt in varying strong magnetic field Or will the domain strct collaps

According to the domain theory, Ferromagnetic substance when kept in the external strong magnetic field, it undergoes magnetisation by Rotation and becomes a permanent magnet thereby even after ...
37 views

### Energy Conversion from Mass to Gravitational Wave

How is mass converted to gravitational wave energy by inspiralling binary black holes? Is the gravitational wave energy coming purely from the kinetic energy/gravitational potential of the two black ...
45 views

### Can photons undergo quantum tunneling?

Most leptons can do this so I'm curious to see if photons or any bosons at all can.
24 views

### Why does the co-efficent of friction between plane and body does change depending on the angle of the plane?

First of all I know there is a similar question to this one. However, it didn't help me resolve my problem. Let's say there is a body on a angled plane and the system is in equilibrium (the body ...
25 views

### Local temperature equation for a planet

After seeing in science fiction too many planets with two suns that look too much like a geocentric system, I'm trying for my own amusement to understand if it's really possible to have a planet with ...
12 views

### How to include temperature effect in optical bloch equations (optical pumping)?

My problem is about the optical pumping of Alkali atoms by circularly polarized pump light. Consider a circular polarized light ($\Delta m=+1$) $$\vec{E}(z,t)= \vec{E}^{(+)}_0 e^{-i\nu t}+c.c.$$ ...
51 views

### Why does vector addition work in physics?

How do we know for sure that vector addition works while working in 2D?Is there a mathematical proof for this?
39 views

### What effect would GW150914 have had over a much shorter distance? [duplicate]

In the wake of the recent news of the confirmation of the existence on gravity waves, I was discussing gravitational waves with a friend, and he asked whether this could potentially lead to some kind ...
18 views

### Light from the big bang [duplicate]

Considering that the Big Bang all started from a single point in space time, and the light emitted from it has been spreading outwards in all directions ever since, how do we, from earth, see the ...
25 views

### How to find the position of a particle in a vector (force) field? [on hold]

Let's say that we have two dimensional space and in it a particle. This space has a vector field which is defined as: $$F = x^2$$ For every 1 unit of displacement in the x direction, the force vector ...
74 views

### Why are magnets not in form of hollow spheres

If magnets were in form of follow spheres, outer surface and inner surface being either north or south pole, then I cannot imagine what would be the field be like. But in that case, every magnet would ...
44 views

### How LIGO is calibrated?

I think I have understood properly the principle of LIGO, however the sensitivty is around $10^{-18}m$ of accuracy of distorion. That looks pretty small... just starting with simpler phenomena, for ...
143 views

### LIGO may have inadvertently detected the helioseismic burst from the Sun on 14 September 2015

Here is a quote from an online article: "A gust is on the way. NOAA forecasters expect a stream of high-speed solar wind to reach Earth on Sept. 14th-15th, sparking renewed displays of high-latitude ...