Timeline for Why do telescopes converge light instead of diverge?
Current License: CC BY-SA 4.0
8 events
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| Nov 24 at 10:31 | history | edited | Whit3rd | CC BY-SA 4.0 |
Add a summary of convergence of light as telescopic.
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| Nov 23 at 17:45 | comment | added | Acccumulation | Also, focusing light generally does not create interference, positive or negative. Interference only exists when there is a coherent light source, such as a laser, a photon in a double-slit experiment, or entangled particles. | |
| Nov 23 at 17:43 | comment | added | Acccumulation | The angle of incidence is a special case of the local minimum, and the local minimum is what causes gravitational lensing (and it's actually space-time that's curving, not the light beam; the light beam only appears to curve because it follows the space-time curvature). Time-of-flight is also a global property, and therefore Huygens' principle does not apply to it. | |
| Nov 23 at 4:54 | comment | added | Whit3rd | @Acccumulation No angle-of-incidence argument is available for (for instance) the gravitational lensing, but the Huygens' principle still applies. It's not the total thickness (a global property) but the time-of-flight between points on each side of the interface that determines the light path (and obeys Snell's law). Huygens principle is more general than Snell's refraction formula. | |
| Nov 23 at 4:02 | comment | added | Acccumulation | The angle of incidence affects the local minimum. The thickness doesn't. The photon has no way of "knowing" what the thickness is when it hits the lens. | |
| Nov 23 at 0:43 | comment | added | Whit3rd | @Acccumulation: In the Huygens picture, it's always a local minimum time that determines refraction. The Fresnel lens has lots of disparate localities, which fail to be smooth/well-behaved at the breaks. Most of the light doesn't hit those narrow breaks, of course. | |
| Nov 22 at 21:56 | comment | added | Acccumulation | It's not thickness, it's angle of incidence. A Fresnel lens can be used for magnification, even though its average thickness is the same in the center as at the edges. | |
| Nov 21 at 18:57 | history | answered | Whit3rd | CC BY-SA 4.0 |