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Light??
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<blockquote data-quote="Harte" data-source="post: 25240" data-attributes="member: 443"><p><strong>Re: Light??</strong></p><p></p><p><div class='quotetop'>QUOTE(\"Alpha and 0mega\")</div></p><p> </p><p>A&O,</p><p>Really excellent questions. That's using the ol' noggin.</p><p> </p><p><strong>1)Does light loses its energy as it travels??</strong></p><p>No. A light beam appears to lose energy because it widens as it travels so the light becomes more diffuse (weaker.) But the total energy in a beam of light stays the same until the beam hits something.</p><p></p><p><strong>2)Is light a matter?can it be attracted by gravitational force?</strong></p><p> </p><p>Light, like everything else in existance, can be considered a wave or a particle. In either case light does have mass. </p><p> </p><p>Gravity doesn't attract anything <em>per se, </em>gravity is defined by Einstein as a curved area in spacetime caused by a nearby mass. Think of how inertia pulls you to the left when you are in a car going around a curve to the right. Inertia tries to keep all motion in a straight line for objects with mass. The moon is always going around a curve (the orbit) but the moon does not feel the inertia trying to tug it back to a straight line. That's because, for the moon, the orbit <em>is</em> a straight line. The spacetime is curved so the straight line is curved. </p><p> </p><p>When we have total solar eclipses, physicist go out and observe the positions of stars whose apparent positions are near the edge of the sun's disk. These stars are actually <em>behind</em> the sun but their light is bent by the curvature of spacetime near the sun and is thus curved around the sun and into our telescopes. The difference between the actual positions of these stars and the observed positions we see them at gives us a measure of this curvature. Einstein's general theory makes very precise predictions about this curvature and, so far, no measure made in this way has differed from Einstein's predictions in the least. So yes, light is affected by gravity in the same way everything else is, but "attracted" may not be the best word to use in describing this.</p><p></p><p><strong>3)As the textbook say,light is reflected.but in the book it show that light is only reflected to a certain angle.IF thats the case,why can we see everything??since not every light is reflected to our direction.</strong></p><p> </p><p>Imagine looking at a flower in the sun. If all the light hitting the flower were reflected back to your eyes, it would be like looking at the sun in a mirror. Light hits the flower. Some of the light is absorbed, some is reflected. The reflected light is not all together, it is a "scattering" of waves/photons of different wavelengths/energy levels. Some reflected light goes into your eyes and you see the flower. Some reflected light goes the other way, over thewre where your friend is standing, and he sees the flower too.</p><p> </p><p>Most books about this are trying to show what a mirror or a lens do to light. Mirrors reflect light very regularly, with very little scattering. But remember, even if you stand off to one side and can't see the image of your friend standing in front of the mirror, you can see the mirror itself.</p><p> </p><p>Hope this helps.</p><p> </p><p>Harte</p></blockquote><p></p>
[QUOTE="Harte, post: 25240, member: 443"] [b]Re: Light??[/b] <div class='quotetop'>QUOTE(\"Alpha and 0mega\")</div> A&O, Really excellent questions. That's using the ol' noggin. [b]1)Does light loses its energy as it travels??[/b] No. A light beam appears to lose energy because it widens as it travels so the light becomes more diffuse (weaker.) But the total energy in a beam of light stays the same until the beam hits something. [b]2)Is light a matter?can it be attracted by gravitational force?[/b] Light, like everything else in existance, can be considered a wave or a particle. In either case light does have mass. Gravity doesn't attract anything [i]per se, [/i]gravity is defined by Einstein as a curved area in spacetime caused by a nearby mass. Think of how inertia pulls you to the left when you are in a car going around a curve to the right. Inertia tries to keep all motion in a straight line for objects with mass. The moon is always going around a curve (the orbit) but the moon does not feel the inertia trying to tug it back to a straight line. That's because, for the moon, the orbit [i]is[/i] a straight line. The spacetime is curved so the straight line is curved. When we have total solar eclipses, physicist go out and observe the positions of stars whose apparent positions are near the edge of the sun's disk. These stars are actually [i]behind[/i] the sun but their light is bent by the curvature of spacetime near the sun and is thus curved around the sun and into our telescopes. The difference between the actual positions of these stars and the observed positions we see them at gives us a measure of this curvature. Einstein's general theory makes very precise predictions about this curvature and, so far, no measure made in this way has differed from Einstein's predictions in the least. So yes, light is affected by gravity in the same way everything else is, but "attracted" may not be the best word to use in describing this. [b]3)As the textbook say,light is reflected.but in the book it show that light is only reflected to a certain angle.IF thats the case,why can we see everything??since not every light is reflected to our direction.[/b] Imagine looking at a flower in the sun. If all the light hitting the flower were reflected back to your eyes, it would be like looking at the sun in a mirror. Light hits the flower. Some of the light is absorbed, some is reflected. The reflected light is not all together, it is a "scattering" of waves/photons of different wavelengths/energy levels. Some reflected light goes into your eyes and you see the flower. Some reflected light goes the other way, over thewre where your friend is standing, and he sees the flower too. Most books about this are trying to show what a mirror or a lens do to light. Mirrors reflect light very regularly, with very little scattering. But remember, even if you stand off to one side and can't see the image of your friend standing in front of the mirror, you can see the mirror itself. Hope this helps. Harte [/QUOTE]
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