how the rate of variability of a source of light can be used to place an upper limit on the size of the source
477256
please explain a little more...
976281
Maybe you want to think along the lines of a change in energy state and a resultant heat ( gain or loss ) absorbing light in a given wavelength range.
666930
less light makes it to your eye
1151404
If the deflection surface has any diffraction or diffusion to it, the light may just be redirected imperfectly. 12kV? Jumpin Gigawatts!
87064
A basic observable quantity for a star is its brightness. Because stars can have a very broad range of brightness, astronomers commonly introduce a logarithmic scale called a magnitude scale to classify the brightness.\nThe Magnitude Scale:\nThe magnitudes m1 and m2 for two stars are related to the corresponding brightnesses b1 and b2 through the equation:\nm1-m2=2.5(logb1-logb2)=2.5log(b1/b2)\nwhere "log" means the (base-10) logarithm of the corresponding number; that is, the power to which 10 must be raised to give the number. Because this relation is logarithmic, a very large range in brightnesses corresponds to a much smaller range of magnitudes; this is a major utility of the magnitude scale.\nThe preceding equation gives us a way to relate the magnitudes and brightnesses of two object, but there are several ways in which we could specify the brightness and this leads to several different magnitudes that astromers define. One important distinction is between whether we are talking about the apparent brightness of an object, or its "true" brightness. The former is a convolution of the true brightness and the effect of distance on the observed brightness, because the intensity of light from a source decreases as the square of the distance (the inverse square law). The apparent magnitude of an object is the "what you see is what you get" magnitude. It is determined using the apparent brightness as observed, with no consideration given to how distance is influencing the observation. Obviously the apparent magnitude is easy to determine because we only need measure the apparent brightness and convert it to a magnitude with no further thought given to the matter. However, the apparent magnitude is not so useful because it mixes up the intrinsic brightness of the star (which is related to its internal energy production) and the effect of distance (which has nothing to do with the intrinsic structure of the star).Clearly, a star that is very bright in our sky could be bright primarily because it is very close to us (the Sun, for example), or because it is rather distant but is intrinsically very bright (Betelgeuse, for example). It is the "true" brightness, with the distance dependence factored out, that is of most interest to us as astronomers. Therefore, it is useful to establish a convention whereby we can compare two stars on the same footing, without variations in brightness due to differing distances complicating the issue. \nAstronomers define the absolute magnitude to be the apparent magnitude that a star would have if it were (in our imagination) placed at a distance of 10 parsecs (which is 32.6 light years) from the Earth. I can do this if I know the true distance to the star because I can then use the inverse square law to determine how its apparent brightness would change if I moved it from its true position to a standard distance of 10 parsecs. There is nothing magic about the standard distance of 10 parsecs. We could as well use any other distance as a standard, but 10 parsecs is the distance astronomers have chosen for this standard. A common convention, and one that we will mostly follow, is to use a lower-case "m" to denote an apparent magnitude and an upper-case "M" to denote an absolute magnitude. \nNotice the very important point that I can determine the apparent magnitude m of a star simply by measuring how bright it appears to be, but to determine the absolute magnitude M the distance to the star must also be known. As we shall see, determining distances to stars is a quite non-trivial matter in the general case.You might think that introducing the apparent and absolute magnitudes would resolve ambiguities about what we mean when we refer to the brightness of a star, but there is a further complication. The brightness of an object (whether apparent or absolute) depends on the wavelength at which we observe it, as we saw clearly in the discussion of
16564
Water magnifies the power of UV rays in light.
537588
1) The original or main light source.Can be increased or decreased.\n\n2) Diaphragm - It can control the diameter of the aperture and thus control the light intensity.\n\n3) Filter- by using suitable colour of the filter one can control the light intensity.
522069
well.. refractive index is a function of frequency
752656
The size of an object you can resolve with an optical system has a theoretical limit given by the wavelenght of the light you're using divided by the diameter of the optics multiplied by 1.22. If you plug the numbers in you find for a 1 foot diameter optical system at visible light (~400 nm) at an altitude of 100km, the smallest thing you could see is on the order of a foot, give or take (rough calculation). You could definitely not read a postage stamp or a wrist watch. Maybe a license plate with some bigger optics, but this is ignoring all sorts of atmospheric scintillation which screws things up.
985833
I think I understand your experiment.  I'm standing at the anulus observing.  I see the light from the lighthouse.  Exactly one second later, I see the next flash of light from the lighthouse, no matter the radius of the anulus.  To satisfy (1) the perimeter of the anulus must be 186,000 miles, the diameter 186,000 miles / pi or 59,206 miles, and the radius d/2 = 29,603 miles.  That's about 7.47 times the earth's radius.  For (2), if you double the radius, you double the circumference.  Keeping the time the same, that doubles the speed.  You already knew that.\n\nFor (3), at the lighthouse you see the reflection of the lighthouse beam.  To reduce confusion, you could do what real lighthouses or bouys sometimes do:  alternating rotations are a different color.  But what you would see is the reflection, but delayed by 1/pi seconds, or 318 milliseconds.\n\nI'm guessing at your response.  At z=2D, this 'intersection' is travelling at twice the speed of light.  There's no physics problem with that.  It's not conveying either matter or information faster than the speed of light.  You have just contrived two events closer in time to each other than the time light would take to go between them.
144703
No, one of the defining properties of a photon is that two or more are capable of simulatenously existing at the same co-ordinates. As such they can't possibly intercept each other or cause refraction since that requires either that they bounce of one another or else slow one another down. Neither is possible if they are to continue being capable of coexiting at the same location.\n\nPhotons can certainly interfere with each other, but only to the extent of increasing or decreasing amplitude, not wavelength or direction. At best you could theoretically reduce the amplitude of one source to zero, thus making it cease to exist, or alternatively boost the amplitude for a stronger signal.
441629
Boy, you are really time-constrained!  What kind of light?  Edison did an experiment on sending sound over light waves, but was limited to visual light, in air (not laser light, in fiber optics like we use today.)  What equipment have you?\nSuggestions, without knowing much:  Send a beam of light as Morse Code and determine the maximum distances based on different times of day, weather conditions, strength of light beam, type of light beam, acuteness of receiver's eyes.  \n\nOr better yet if you are a computer geek  :), do it with a photo cell as the receiver and send the signal to a computer for analysis and conversion into text.\n\nGood Luck!  Let me know your results!
138271
This question has two different answers depending on how you read it.  The intensity of the light that reaches you will be reduced as you move away from it, but the intensity of the source stays constant.  Its a matter of perspective, so therefore the preson who asked you this question should clarify it for you.  I'd write both answers and explain each.  Your teacher should except that.
1006016
Laser interferometry may be what you are looking for
576638
La detectacion de luz ,como photon o como onda, depende del typo o metodo de experimento para explorar la naturaleza de la luz. La luz exhibe la characteristica de honda en experimentos de diffraccion e interferencia y exhibe characteristicas de particula en experimentos de ionizacion de atomos con radiacion de varias energias. La luz se mueve en linea recta a menos que es reflejada o desviada por el medio atraves cual viaja. La luz que proviene de estrellas y galaxias distantes provee informacion soble la velocidad de esas estrellas y galaxias porque la luz como onda es cambiada como es cambiado el sonido de un tren qhe primero se aproxima y despues se aleja. ( vea terminos como "red-shift" and "doppler effect") El sonido aumenta cuando el tren viene y despues mengua cuando el tren se va.
8548
Close.  I would say it's because the photons from the object hit a smaller area of the cornea.  If you think of the surface of the cornea as a screen onto which the world in front of the viewer is projected through a lens, as an object is moved away the angle between its top and bottom gets smaller and so the relative size of the object in that projection gets smaller.
1103364
each magnitude corresponds to a ratio of 10^(-.2), so you want to multiply the (-.2) by (1.9) and look at 10 to that power. This gives the  fraction of photons that make the trip.\n\nHomework and repeat question.