4621

Physics, Astronomy & Cosmology / How are muons detected and generated?

« on: 12/07/2017 06:36:20 »

Does anyone has reference to :
How to detect muons?
How to generate them in a lab?
How to distinguish between muon and other particles?

4622

Physics, Astronomy & Cosmology / Re: Can the Compton equation be represented as a vector?

« on: 12/07/2017 04:41:11 »

Yes Evan, you are correct.
Of course the tetrahedron does not give a direction, unless one point is assumed to be the tail of the vector.
The tetrahedron I speak of has four surfaces and six edges (as all tetrahedra do). Each surface is a right triangle.
One edge is the magnitude, three edges correspond to vector components, and two edges may be called sub-components.
regards
rich

You can not have a finite tetrahedron with all surfaces being right triangles.

4623

Physics, Astronomy & Cosmology / Re: Is ultra violet light from the sun polarised? If so, why?

« on: 08/07/2017 07:04:58 »

To further answer the OP's question about 'how' light becomes polarized:

We have covered the fact that light becomes polarized by reflection, and that polarized sunglasses are designed not to allow these reflective glares to pass through the lens of the sunglasses, however...

Light can also becomes polarized by refraction, as stated in Fresnel's equation.
https://en.wikipedia.org/wiki/Fresnel_equations

4624

General Science / Re: How can I stop static building up on my body?

« on: 04/07/2017 13:27:11 »

...
- Move to a climate with higher humidity.

Or maybe install a humidifier in your room.

4625

Physics, Astronomy & Cosmology / Re: How are the results of the double slit experiment recorded?

« on: 04/07/2017 07:15:29 »

I guess what I really tried to ask wasn't made clear, and perhaps even now it still doesn't make sense?

I watched this short animation 

When scientists try to 'observe' the interference pattern, it resorts back to the original non interference pattern. It's as if it knows it is being observed/watched.

But I was wondering, how do scientists know about the non interference pattern? Surely it is through observation/being watched?

If you watch the video and understand my question, then great. If my question doesn't make sense then ... thanks for reading and for the answers above already given.

A problem in representing an experiment using animation/simulation/model has a merit, which is simplifying the learning process by reducing the number of parameters/factors that influence the result, so students can be more focus on the targeted factor. But it also has its own cost, which sometimes overwhelms the benefits and missing the intended goals, or even showing the wrong results.
For example, I found some learning materials in youtube which shows light dispersion by a prism producing rainbow pattern, but the order of the colors is reversed.
I saw some problems in the video above. First, passing light through a single slit apparatus produces diffraction pattern, instead of a single bright line. Second, it doesn't show the actual method to observe the photon going through each slit. In some papers I've read regarding this experiment, they use polarization filters with different orientation for each slit (e.g. vertical for the left and horizontal for the right, or using clockwise and counter clockwise polarizers). So if we can detect the polarization state of the photon on the screen, we can conclude which slit it has passed through.
But of course we wouldn't get fringes on the screen, because lights with different polarization state don't produce destructive interference.

4626

Physics, Astronomy & Cosmology / Re: How are the results of the double slit experiment recorded?

« on: 03/07/2017 12:40:46 »

If we assume that light is stream of particles, just like Newton did, the occurence of light and dark bands on the screen is an unexpected result.
If we assume that light is a wave, akin to wave of water surface, then the unexpected result will show when the intensity is extremely low,  undetected by naked eye, hence requires very sensitive sensor, such as photomultiplier.

4627

Physics, Astronomy & Cosmology / Re: How are the results of the double slit experiment recorded?

« on: 03/07/2017 12:34:05 »

In my topic https://www.thenakedscientists.com/forum/index.php?topic=66301.0
I show double slit experiment, which is just a special case of diffraction with four edges obstruction.

4628

Physics, Astronomy & Cosmology / Re: What is the effect on the moon's orbit of harvesting tidal energy?

« on: 21/05/2017 04:51:59 »

According to my calculations, the Moon gains about 3.826 x 10^18 joules from the Earth due to tidal action every year. It gains 7.564 x 10^18 joules of gravitational potential energy due to the increase in distance from the Earth (3.82 centimeters per year) and loses 3.738 x 10^18 joules of kinetic energy due to the slowing of its orbital speed. That assumes I didn't make any kind of calculation error. The Moon has been doing this for billions of years and will continue to do it for hundreds of millions of years yet. Of course, the rate has varied in the past (it would have taken energy from the Earth at a much faster rate in the distant past when it was much closer to the Earth). In the future, that rate will slow down. The rotational kinetic energy of the Earth is 2.138 x 10^29 joules.

It's pretty safe to conclude that nothing humans could do in the immediate future would come remotely close to exhausting such a resource.

Thanks for your effort. Can you share your calculation?
Did you calculate based on earth-moon barycenter? IMO, when the moon is moving away from earth, it also means that the earth is moving away from the barycenter too, which makes total potential energy of the system increase.

4629

Physics, Astronomy & Cosmology / Re: What is the effect on the moon's orbit of harvesting tidal energy?

« on: 20/05/2017 17:05:51 »

For 1 Joule tidal energy harvested

There is a huge amount of tidal energy involved in daily flexing the solid Earth, and dragging the world's oceans across their ocean floors.

If we harvested 1 Joule (or 1 TJ) of this energy, it would make an insignificant change in the amount of energy lost to tides every day.

ok, let's make it 1 terajoule.

4630

Physics, Astronomy & Cosmology / Re: What is the effect of energy harvesting tidal wave to the moon's orbit?

« on: 19/05/2017 12:55:06 »

For 1 Joule tidal energy harvested, how much earth's rotational energy lost, how much loss in moon's kinetic energy, how much gain in moon's potential energy?
How about earth's potential energy?

4631

Physics, Astronomy & Cosmology / What is the effect on the moon's orbit of harvesting tidal energy?

« on: 19/05/2017 10:32:29 »

Harvesting energy from tides is known to make the Earth to rotate slower, but what is the effect on the moon's orbit? Measurements shows that the moon is moving away from Earth, but that means its potential energy is increasing?

4632

Science Experiments / Re: How do microwaves behave?

« on: 06/05/2017 09:03:31 »

The difference between multilayer flat strips in the last video and multilayer metal grating which produces "normal" refraction seems to be merely due to the lack of longitudinal conductor component in the flat strips. So I plan to investigate further about longitudinal propagation in microwave in the next videos.
Do you have any idea about how could this be done?

4633

Physics, Astronomy & Cosmology / Re: Is the twin paradox real?

« on: 06/05/2017 08:25:11 »

...
You will never have a situation where the rocket and any clock that it is passing will disagree as to what their respective clocks read as they passed each other.

Let me summarize your analysis to make it easier to read.

According to earth's (and stationary clocks) reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
the rocket then turn around
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.

According to rocket's reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
the earth then turn around
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.

4634

Physics, Astronomy & Cosmology / Re: How fast can light be polarized?

« on: 06/05/2017 07:45:27 »

A circularly polarized wave is basically a constant electric field with polarization direction rotated as fast as its frequency.
So the question can be rephrased, how fast can the magnitude of a circularly polarized wave modulated?
https://en.wikipedia.org/wiki/Circular_polarization

4635

Physics, Astronomy & Cosmology / Re: Is the twin paradox real?

« on: 06/05/2017 05:12:16 »

as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.

You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?

I need to make a correction to the scenario above. In order to make the rocket twin ages at 80% rate, he has to go at 0.6c, hence the time dilation factor would be 0.8.
So to make the rocket pass the first clock at 1 second, the distance between adjacent clocks should only be 0.6 light seconds. But the argument is still intact.

4636

Physics, Astronomy & Cosmology / Re: How do forces apply between two wires both carrying current?

« on: 05/05/2017 06:34:00 »

Newton's third law is an implication of momentum conservation law.

4637

Physics, Astronomy & Cosmology / Re: Can an electromagnet erase a permanent magnet?

« on: 04/05/2017 14:27:27 »

when a magnet is reversed, what is actually changed? is it electron spin of the atoms in it? or electrons motion around atoms' nuclei? or electrons motion around the crystal lattice? or spin of the nuclei themselves?

The magnetic domains rearrange.

Let's say I have a microscopic permanent magnet cube containing 3^3 domains (imagine Rubik' cube). At first they all directing upward.
After electromagnetically reversed, what happens to the atoms in the interface between adjacent domains? Are they sliding to each other?

4638

Physics, Astronomy & Cosmology / Re: What makes something transparent?

« on: 04/05/2017 14:12:44 »

Here's a pretty good explanation: https://physics.stackexchange.com/questions/7437/why-glass-is-transparent

In a nutshell, it is due to the absence of atomic structures that can absorb light in the visible frequency range.

transparency is not exclusively determined by atomic structure. It's also affected by molecular bond/structure, as shown in Infrared spectroscopy.
When light hit a material, several things might happen to it:
- it is passed through
- it is reflected
- it is absorbed
when passed or reflected, light can also be refracted, polarized, diffracted, scattered.
when absorbed, it is converted to other form of energy, such as heat, chemical, or electrical. It can also converted to different frequency of light, as found in fluorescent materials.

4639

Physics, Astronomy & Cosmology / Re: Can an electromagnet erase a permanent magnet?

« on: 04/05/2017 14:01:52 »

when a magnet is reversed, what is actually changed? is it electron spin of the atoms in it? or electrons motion around atoms' nuclei? or electrons motion around the crystal lattice? or spin of the nuclei themselves?

4640

Physics, Astronomy & Cosmology / Can an electromagnet erase a permanent magnet?

« on: 03/05/2017 12:30:25 »

Can we demagnetize a permanent magnet by applying electromagnetic field in reverse polarity?