Questions?

[Guest liliangrn]

Hi Clay,

 

So terminal velocity is dependant on the altitude of the surface you hit. The highest speed of terminal velocity would be when you hit water level. This is the closest to the centre of gravity you can fall. Unless the bottom of the grand canyon is below sea level. Do you know the altitude of the Grand Canyon?

 

Josephine

[C1ay]

Do you know the altitude of the Grand Canyon?

I think I read somewhere that it is around 7000 feet....

[Turtle]

___The Grand Canyon is just over 1 mile deep at the deepest. I once hiked to the bottom and back while studying geology. It was 110 degrees F at the bottom; took me from 6 am to 6 pm. The trail in is not the trail out as the trail in has no water.

___Some of the oldest rock known (schist) on Earth is at the very bottom. I don't know what the altitude(rim or bottom) is. Death Valley however is some 50 feet below sea level if I remember correctly.

___Light will bend inside glass when the incident ray is perpendicular to the surface. The type of glass determines the angle of bending. This also is why optical mirrors must be front surface mirrors & not the common back surface mirrors as in vanitys. ;)

[Buffy]

___Some of the oldest rock known (schist) on Earth is at the very bottom. I don't know what the altitude(rim or bottom) is. Death Valley however is some 50 feet below sea level if I remember correctly.

Current actual altitude of course does not directly correllate to age, since as you well know, our tectonic plates are getting tossed up and down (know you know this Turtle, this is a clarification for the audience....)

 

Cheers,

Buffy

[Turtle]

___No no...of course not. We were talking about the altitude in relation to terminal velocities. The farther you fall the higher your terminal velocity.

___I only threw in age because that's whats' at the bottom of Grand Canyon, some of the oldest rocks on Earth(about 3,5 billion years old schist if I recall.

___The law of superimposition does hold in general however, ie the lower in the strata the older. One of the major breakthroughs in geology in its early beginnings in fact. ;)

[Guest liliangrn]

Thanks Turtle,

 

___Some of the oldest rock known (schist) on Earth is at the very bottom. I don't know what the altitude(rim or bottom) is. Death Valley however is some 50 feet below sea level if I remember correctly.

 

Can I make your job harder by asking is this at high tide or low tide? Just kidding.

 

___Light will bend inside glass when the incident ray is perpendicular to the surface. The type of glass determines the angle of bending. This also is why optical mirrors must be front surface mirrors & not the common back surface mirrors as in vanitys.

 

I don't understand. If I flash a light on a tangent it will bend toward the normal line as the site I linked said. This is why I asked the question: which way would a perpendicular light bend since it's, apparently, already travelling the normal line.

 

Josephine

[Turtle]

___Good point on the tide factor. I don't know how science handles that, but in property that is coastal the measurement is usually 'Mean High Tide' & established through measurement records. Up the coast of Washington, some beach areas have accrued & there is large dispute whether it belongs to coast property owners, the County, or the State. Further, since it seems sea levels are rising, what happens then?

___I often listen to the local airtraffic control tower & when the contact incoming planes they give the airports altitude & noticed it changed! I finally realized the planes altimiters are really barometers & they need to 'zero' the onboard altimeter to the barometric reading at ground for the airport.

___I wonder how this all relates to how they callibrate the GPS system?

___Back to the light beam; I neglected to read the link at first...ooopppss. Anyway, I think I see your point now, almost like the light beam is deciding something then? Maybe is has to do with the crystalline structure of glass. Also, it may bend so as to form a halo, ie. bending equally in a ring? Just some thoughts. ;)

[Guest liliangrn]

I wouldn't have a clue on the light thing ;) . I guess still water would be a better example than glass because you wouldn't have the glass composition to worry about. But you are probably right that it bends somehow. If you were looking at it on an angle it would probably appear bent anyway. There we go I solved it. LOL

 

Interesting facts on the tide stuff aswell. It affects more people than surfers and us girls with PMS. Lol ;)

 

Thanks Turtle

[Qfwfq]

wherein it is often claimed they have a terminal velocity of under 200mph. In point of fact, the USAF in the fiftys hauled a guy up to 100,000 feet on a ballon & then he jumped off & before opening his chute he broke the sound barrier!

TV is an aerodynamic issue, the condition is air friction compensating weight. In a sense it means the air friction reduces g to zero.

 

Obviously it depends on altidude so it decreases as you come down fro 100,000 ft, the speed of sound also varies with density, that guy must have reached a great speed while high which then became supersonic bfore he had slowed down enough.

 

I hope his chute withstood the stress!!!

 

P. S. ah, yes, I meant to say, a skydiver will fall a lot slower with arms and legs spread horizontally than when in an upright position, attention-style.

[Qfwfq]

Light will bend inside glass when the incident ray is perpendicular to the surface.QUOTE]No, not when perpendicular. The rule, using angles between the light and the normal to the surface, is that the ratio between the sines of the two angles is given by the ratio between the indices of refraction.

 

Work it out, for when the incoming angle is zero.

[Guest liliangrn]

Just to make a correction on my previous statement:

 

Light has no inertial mass. That is a KNOWN fact supported by a

gazillion empirical tests.

 

This is a wave effect. The speed of light itself is medium dependent.

The constant "c" is spoken of as "the speed of light in vacuo". But

actually the fact that light moves at c in the vacuum is really only a

side effect of what c really means. It is fundamentally the limiting

speed at which *information* can move from one point to another in

observable spacer. Light, having no inertial mass therefore moves at

this maximum possible speed. (another fallacy is that nothing moves

faster than light. In fact some stuff can, as long as you can't see it

happen on principle)*

Now, in a transparent medium such as air, water or glass, the speed of

information itself is less.** That is, c itself is less. Light *still*

moves at the speed of information *in that medium*. Then the wave nature

of the light produces that well known effect of refractive bending as

the waves have to close up to retain their correct energy at the new

value of c.

 

You do not of course see this shortening of wavelength, because you

cannot actually see light. What you see is an image of a light source,

which includes a scattering medium, so we can see objects, but light

itself is invisible

 

The speed is still c. The shorter the wavelengths the longer

light takes to travel the same path. If you could walk along the shorter

wave lengths it would be a much longer path than walking along the

longer wave lengths (If you were travelling at a constant rate along

both paths from point A to Point B. A to B would be a straight line).

 

The so called speeding up and slowing of light

experiments of late do not apply to the actual light waves themselves,

but to what is known as their "group velocity" which is related to their

phase. Say you have a long wave packet whose peak is near the front.

Now if you can make that peak move to the back of the packet, it looks

as if the light has slowed down if all you are looking at is the peak.

 

It has to do also with the density of the medium they are passing the light through as well. The article stated that the experiment could only be done at near absolute zero.

The atoms they are using as a medium are so dense at such a temperature that light waves would be naturally

slower to begin with. Add to that the 'group velocity' and voila, you

can appear to stop light all together for the breifest of moments.

 

Similarly, if you have a wave packet with the peak towards the back and

move it forward, (I'm not too sure how they actually do this, but this

is actually how it works), again if you are only reading the peak, it

looks as if you've made light go faster than c, whereas in fact you

haven't.

 

*Galaxies at about two billion light years and further beyond the Hubble

limit move faster than light.

 

Now I'm leaving!

[Kirk Gregory Czuhai]

Just to make a correction on my previous statement:

 

 

*Galaxies at about two billion light years and further beyond the Hubble

limit move faster than light.

 

Now I'm leaving!

Well, well..

:circle: well i am not going to debate that now ... :shrug:

 

but if you want to make something move faster than the speed of light, point a small

flashlight at one edge of the full moon and scan it back and forth across the moon's

surface from the earth from one edge to the oppositie's back and forth fairly quickly.

you will be making a paths of photons in a couple of seconds on the moon spreading them

faster than the speed of light!

 

the refration of light ocurring as light travels from say air to water or bounces around

in a diamond ring (a fancy piece of coal! [carbon]) obeys:

 

Snell's law,---------------> n1*sin(theta2)=n2*sin(theta1) with n2>n1

the n's are called the refractive indicies of the medium and

(medium 1,air) and generally are the ratios of the speed of light in the medium

divided by the speed of light in air at STP.

(medium 2, light speed less than air's)

 

in elementary physics courses snell's law is just accepted as fact but if you

would like a classical physics proof of it treating light as an electromagnetic wave

see Jacksons text, "Classical Electodynamics".

 

Now for the case of "tired" light, i.e. moving "up" through a gravitational field, this is the

same as a de-acceleration due to the equivalence principle of gravitational physics which

has been experimentally verified mucho!

 

Now since photons only exist and travel at the speed of light in the medium they are in,

the only way they could lose energy E=hf would be for them to lower their frequency which since v=wavelenth*frequency for any wave c=wavelenth*frequency of the light and

thus the light become more "red" lower in frequency and its wavelength increases to

keep the c constant.

 

peace and love,

and,

love and peace,

(kirk) kirk gregory czuhai LOVES !

p.s.

the astute reader will see upon reflection upon Snell's law why the lakes and pools look

shallower to the eye than they really are and also,

that there exist a criticle angle of incidence theta,c for rays from medium 2 such that

all rays are refracted/reflected BACK into medium 2! Such is the Stuff of what optical

cable is all about!!!!

[Damo2600]

I am merely an amatuer (so forgive me) but most of this post appears to be physics 'chinese' to me.

 

The torch experiment made no sense to me. If I shake a flash light the photons still move at c. No?

 

"Now since photons only exist and travel at the speed of light in the medium they are in,

the only way they could lose energy E=hf would be for them to lower their frequency which since v=wavelenth*frequency for any wave c=wavelenth*frequency of the light and

thus the light become more "red" lower in frequency and its wavelength increases to

keep the c constant."

 

You didn't explain why the wavelength, rather than the frequency, couldn't change. It would make a lot more sense to me that if the wavelengths of light are shorter. So the light leaving the pool would revert to the air medium wave length. So the light leaving the water from a shorter wave length to a longer wave length would not affect frequency. The fact that light is bent suggests to me that the pool is shorter than it is.

 

So this is where you get a change in velocity of light by stating that the frquency changes and not the wavelength. If the frequency changes and not the wave length that means that light changes velocity. You can't just say that light can't change wave length without stating why. I will have to look into this...

 

Damien

[Damo2600]

Hey guys I'm back,

 

The wavelength of light in water does change. The wave length can be calculated thus:

 

Wavelength of light in water = wavelength of light in vacuo / n

 

Where n equals the refractive index of water.

 

The following site describes the Refractive Index of water in exceptional degree.

 

http://www.philiplaven.com/p20.html

 

This site shows how a microscope uses shorter wavelengths to see an object upclose by refracting light.

 

em-outreach.ucsd.edu/web-course/Sec-I.A/Sec-I.A.html -

 

This site explains in detail the different frequency of elctro magnetic rays and the ones that are dangerous for you (I've thrown this in for interest)

 

http://micro.magnet.fsu.edu/optics/lightandcolor/electromagnetic.htmlhttp://micro.magnet.fsu.edu/optics/lightandcolor/electromagnetic.html

 

I couldn't find a site, YET, which directly states what I am trying to show. The pool shows the bottom of the pool as being closer than it is. The microscope site explains that a shorter wavelength will make an object appear closer than it is. This can only be achieved by refaction as in the water case. The case is not closed however I must seek out a more effective internet site that explains this case better. I do feel the case is almost closed however.

 

Damien

[Tormod]

I posted a refractive index link in one of your other threads.

 

I am closing this thread as there are now at least three threads about the speed of light.