1. X

    Diffraction grating vs double-slit experiment to calculate light's wavelength?

    Usually, a grating is used over the double-slit experiment because the fringes are narrower so measurements are more precise. However, for a classroom experiment, because less fringes fit onto a piece of paper as the screen with the diffraction grating experiment than the double-slit...
  2. X

    How can you show with a diagram that diffraction is at a maximum when the slit width is equal to the wavelength?

    Usually a diagram will be given like this But how can you show with a diagram that diffraction can be maximised when the slit width is of the order of the wave's wavelength?
  3. K

    Reflection angle help please!

    Could someone tell me what angle I need to place the mirror at to get the reflection at the angle show? Thank you!
  4. S

    Galaxies are seperating faster than light?

    What? If that were true, our galaxy would be moving faster than light. Why aren't people making a bigger deal about the gaps between galaxies expanding faster than light? If the galaxies aren't actually moving that fast implies nothingness has a variable of distance that doesn't actually...
  5. P

    Light diffracting around objects

    What causes light to bend around corners? Is this cause by the gravity of the object? Even though the gravity of the object is relatively small, the light waves are able to pass by it very closely. If you shine a laser close to a metal rod, will it diffract light more so than that of a plastic...
  6. G

    Creating a laser light sheet

    I am attempting to create a laser sheet that I can project through my transparent apparatus so that I can image the illuminated plane. I have been looking into several different ways to get a laser sheet but I'm not super confident with what I have come up with. I've attached an image that...
  7. O

    Light intensity over a specific distance

    Hi guys, I’m looking for some help if any of you would be kind enough (Bigsmile) I am trying to calculate how many lux/lumens an LED needs to be in order to reach the end of a long tunnel then reflect off a mirror and travel up a short distance and the light be seen at the end point. I’m...
  8. M

    Strange optical effect related to light passing through a mesh?

    I hope someone here can explain this curious light effect. (I am brand new here, I just got online and searched for optics forum and this site showed up) Some background: I have a table with a laptop on it, and a chair sitting here that has a mesh back on it that has a pattern of ~2mm holes...
  9. L

    Camera obscura: light behavior

    Hello everybody! Sorry in advance for my wrong terminology. I'm Luca from Italy and I have a question about a pinhole camera. As it was designed, the angle of view is about 111°. But the light cone "touches" the surfaces A and B inside the camera. Question. What will it happen to the...
  10. N

    Light projecting images

    Hi, I'm currently working on a project the aim of which is to build a small night light that uses LEDs. On top of this is a plastic sheet with a design printed on it that is to allow the images to be displayed on the ceiling - but I cannot get it to work! I have tried amending the mode of...
  11. E

    adding two (or more) light beams together

    HI! I'm new to this forum and I don't know if this question belongs here, if not please let me know. I have a project (dormant since I didn't find the solution to this, yet) of modifying a 16mm film projector, one of the mods is to change the light source (incandescent bulb) for a LED, the...
  12. GatheringKnowledge

    Light Clocks and Relative Motion

    I have couple questions about the time, measured by 2 light clocks in a frame, which moves at a constant velocity - where one clock is perpendicular and second one is parallel to the direction of motion...
  13. D

    Does dark matter bend light?

    Does dark matter bend light?
  14. L

    How do you determine the speed of light.

    How do you determine the speed of light?
  15. L


    Do you think the reason that so much is being concealed is to protect the human race with to much knowledge since knowledge can be so destructive? Do you think that it could rain in the proverbial mushroom soup catastrophe with Yukon crakers?
  16. L

    Huygens' T&R mechanism of light

    Huygens describes the transmission and reflection effects of light (fig 5 & 6) using spherical waves generated by the transmission and reflection surface AB. "If one considers further the other pieces H of the wave AC, it appears that they will not only have reached the surface AB by...
  17. L

    FRESNEL DIFFRACTION DERIVATION THAT est. the wave theory of light

    Fresnel derives a diffraction intensity equation by summating the interfering light waves' amplitudes, at the diffraction screen, using a line integral (equ 1). "Hence the intensity of the vibration at P resulting from all these small disturbances is { [ ʃ dz cos (π z2 (a + b) /...
  18. L

    THE speed of light in sofar as the determination is

    Roemer (1676) is accredited as the first to measure the velocity of light but Roemer's calculation of the velocity of light is based on Io forming four eclipses at L, K, F and G but Roemer does not indicate the dates of all four eclipses that are used to calculate the velocity of light since it...
  19. L

    Roemer's measurement of the velocity of light

    Roemer's calculation of the velocity of light is based on an observer on the surface of the earth propagating from L to K on the left side of figure 2 and an observed, on the surface of the earth, that propagates from F to G on the right side of figure 2 where Io forms eclipses at positions L...
  20. avito009

    Does Light obey Newtons First Law?

    We know that Light travels slower in mediums other than vacuum. Scientists were able to drag light to the speed of sound. We know that drag is a force. So is it not drag that slows the speed of light in a fluid? Newtons First Law states: An object...