Some doubts in huygens' principle???
The point of confusion comes in the difference between a wave and a wavefront. The principle specifically speaks of the advancing wavefront, Although waves may be thought of as traveling in all directions, the wavefront is advancing with a shape determined by the original source. Think of the wavefront as the surface of the expanding shape of the volume which is influenced by the waves. For example, a point-source of light would have a spherical wavefront around it of space that is illuminated by the light from that source, whereas a florescent tube would have a cylindrical wavefront expanding around it; the wavefront happens in the moment immediately after turning on the light. Huygens' Principle addresses only the shape of the expanding wavefront, not the waves themselves. The model you were given is confusing also. Huygens' Principle applies in a vacuum. The description you were given says that you can treat each particle as a new source of waves, but that doesn't mean they actually are. That is just one way of visualizing the model that allows you to see that advances through a medium at a speed determined by the medium. Note that the principle applies to sound as well as light. The model allows you to see that the shape of the wavefront may have to change when the wave advances into a medium with a different speed. That is the case of the waves from earthquakes passing through the different layers of the earth's interior. ---------------- damocles:So, in reality, if we consider a wave coming from a source, after this wave passes through a point, we just say that this point is a fresh source of waves as, because the wave passes through that point, the wave APPEARS TO ORIGINATE from that point? Yes. That explains the shape of waves passing a barrier, such as surface waves in water as they propagate around obstacles.
How do you pronounce Huygen's?
Whenever you encounter a Vietnamese name, use the French pronunciations since this is how the language become romanized from former colonist. When in doubt, just ask nicely since most of them will NOT correct you if you got it wrong. So it will be pronounced Huen.
Who discovered Planets? Hindus or Galileo, Huygens or Cassini?
In Geography it's mentioned that Galileo, Huygens and Cassini discovered planets for the first time in 1610, 1665 and 1671 respectively!! I really wonder how true is it?!! Bcos in olden days, apprx.9 lakh years ago (Ramayan happened 9 lakh yrs ago and Planets have been mentioned even there.) Hindu Sages and Scholars already mentioned abt the presence of 9 Planets exactly (they used to call Nava Grahas. Nava=9 Grahas=Planets), their movements and character of these Planets in Books!! Then how come these Galileo, Huygen and Cassini took the credit of discovering the Planets?? And why dont anyone oppose to modern discovery and say that Planets were discovered even before their discovery by these Mathematicians/Astronomers!!
How close were Huygens and Hooke from deriving universal gravitation before Newton?
What it boils down to is that Huygens and Hooke had the right ideas and a generally sound physical intuition about this problem, but they simply couldn’t treat non-circular orbits in a mathematically rigorous way because they didn’t have the calculus.Modern calculus was developed independently by Newton and Leibniz. When Newton’s Principia, with its derivation of the law of universal gravitation, came out in 1687, his mathematical work on the infinitesimal calculus was all unpublished, so that Huygens and Hooke could hardly have been in a position to use it. Leibniz had started to publish his own work on calculus in 1684, but it was initially regarded as very difficult to understand. Moreover, the efforts of Leibniz and his immediate followers to apply his “analytic” formulation of the calculus to mechanics were not very successful. Newton’s own conception of the calculus was based on the geometry of motion, which helps to explain why he accomplished so much as a physicist.Huygens and Leibniz were further hampered in their work on gravitation by the philosophical conviction (which went back to Descartes) that celestial mechanics had to be explained in terms of vortices of a cosmic “subtle fluid” carrying bodies around in their orbits around the Sun. Hooke had no such prejudices. Hooke had also conducted experiments with a spherical pendulum and with a ball rolling around on an inverted cone, which gave him a good intuition for what’s now called the “central-force problem”. What Newton had that Hooke (and almost everyone else) didn’t was an understanding of calculus.A theoretical physicist and amateur historian of science who’s written extensively about Hooke’s work on orbital mechanics is Prof. Michael Nauenberg, of the University of California at Santa Cruz. You can find many of his writings on the subject in his personal webpage.
How is the Cassini–Huygens mission test the theory of general relativity?
While en-route to Saturn and on the other side of the sun from Earth there were some very sophisticated tests of radio waves being bent by the sun’s gravity and these tests confirmed General Relativity’s predictions to an accuracy of 20 parts per million. See the article from JPL at:Saturn-Bound Spacecraft Tests Einstein's Theory
Why do Newton and Einstein say light is a particle, and Huygens and Young say light is a wave?
Photons (light) exhibit a behaviour known as ‘wave-particle duality’, which means that under certain conditions they behave as waves, and under others they behave as particles.Einstein demonstrated that light was a particle in his work on the photoelectric effect, for which he won a Nobel prize. He showed that light was quantised, i.e. it was comprised of discrete ‘packets’ of energy, rather than a continuous stream. By firing light at a metallic surface, it can be seen that the photons knock electrons off the surface at the same speed, regardless of the intensity of the light, which is what you’d expect from a particle. If light was a wave, a more intense beam would result in faster moving electrons.This is in direct conflict with one of physics’ most famous experiments: Young’s Double Slits.Imagine a pond with a barrier across the middle. The barrier has two breaks in it where the water can cross through. If you drop a stone into the water, ripples (waves) will propagate out towards the holes in the barrier and pass through. On the far side of the barrier we will end up with two sets of waves, one from each hole. As the two sets of waves meet and mingle, they will interfere with each other, causing a pattern. Where peaks in the two sets of waves coalesce, the pattern will be twice the height (amplitude) of the original peaks. Where a peak from one set of waves meets a trough from the other set, they will cancel each other out. This is known as an interference pattern.Now try something else. Take a sheet of cardboard with two slits in it and hold it flat. Then drop stones randomly through the holes. They will make two neat piles on the floor (OK they might merge a bit, but there will still be two distinct piles).Now, if you replace the stones with light, you will NOT see the two neat piles, as you would expect if light were a particle. Instead you see an interference pattern of bright and dark strips, just like the waves in the pond.So we see here a contradiction: for Einstein there was concrete proof that light was a particle, whereas Young proved beyond doubt that light was a wave. The only solution? Light can behave either as a wave or as a particle, depending on the experiment being performed. Weird? Welcome to quantum physics.
Which is correct, "I have a doubt" or "I have a question"? Why?
In my view, ‘I have a question’ is better grammatically but it depends on what you’re trying to say here. If you simply want to ask someone a question and get some information, it’s correct to say ‘I have a question.’ However, if you are not sure that what someone is saying is true or correct, then you could say, ‘I have some doubts about what you are saying.’ This is not a question. It’s a comment. We don’t usually say ‘I have a doubt.’ ‘I have some doubts’ is better English. You can also say ‘I doubt that what you’re saying is true.’
A doubt on refraction of visible light in prism?
Well, the doubt is this - Suppose you pass a white light through a prism. Refraction would occur and you would see seven different colors on a sheet of paper placed on opposite side. You'll see that all these colors are placed in a row because each color has different angle of refraction. The pattern would be - Violet, Indigo, Blue, Green, Yellow, Orange, Red. SO ULTIMATELY WHY THEY ALL HAVE DIFFERENT ANGLES OF REFRACTION? My senior says it is because each ray of different color has different velocity. This seems wrong because speed of light (whether red , blue, etc.) in one particular medium is constant. Consequently in prism, each ray should have same velocity. What's the correct reason then? Is it something related to wavelength and frequency of each ray? Because you know red ray has longest wavelength and blue ray has shortest wavelength? PLZ answer this.