Lloyd's mirror
Encyclopedia
Lloyd's mirror is a classic optics
experiment and was first described in 1834 and again in 1837 by Humphry Lloyd in the proceedings of the Royal Irish Academy of Science. In the experiment, light from a monochromatic slit source reflects from a glass surface at a small angle and appears to come from a virtual source
as a result. The reflected light interferes with the direct light from the source, forming interference fringes.
into both. Place a screen about three meters from the laser and adjust the position of the two lenses so that the smallest possible spot can be seen on the screen. Lay a microscope
slide between the two lenses. Carefully raise the slide until the laser beam just grazes its upper surface. A second spot will appear on the screen, about one inch above the first. Remove the converging lens without disturbing the other apparatus. With this lens removed, the cones of light coming from the direct and reflected sources partially overlap, forming an interference pattern on the screen. Details can be found in the experiments using a helium-neon laser.
This interference pattern was used with radio telescopes located along the Australian coastline, using the sea instead of the microscope slide in the optical experiment. This allowed the first interferometric measurements of astronomical objects.
operations.
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
experiment and was first described in 1834 and again in 1837 by Humphry Lloyd in the proceedings of the Royal Irish Academy of Science. In the experiment, light from a monochromatic slit source reflects from a glass surface at a small angle and appears to come from a virtual source
Virtual image
In optics, a virtual image is an image in which the outgoing rays from a point on the object always diverge. It will appear to converge in or behind the optical device . A simple example is a flat mirror where the image of oneself is perceived at twice the distance from oneself to the mirror...
as a result. The reflected light interferes with the direct light from the source, forming interference fringes.
Example experimental setup
Place a converging lens about 10 cm in front of a diverging lens. Shine a laserLaser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
into both. Place a screen about three meters from the laser and adjust the position of the two lenses so that the smallest possible spot can be seen on the screen. Lay a microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
slide between the two lenses. Carefully raise the slide until the laser beam just grazes its upper surface. A second spot will appear on the screen, about one inch above the first. Remove the converging lens without disturbing the other apparatus. With this lens removed, the cones of light coming from the direct and reflected sources partially overlap, forming an interference pattern on the screen. Details can be found in the experiments using a helium-neon laser.
This interference pattern was used with radio telescopes located along the Australian coastline, using the sea instead of the microscope slide in the optical experiment. This allowed the first interferometric measurements of astronomical objects.
Underwater acoustics
An acoustic source just below the water surface generates constructive and destructive interference between the direct path and reflected paths. This can have a major impact on sonarSonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
operations.
External links
- Lloyd's Mirror @ wolfram
- Java Demonstration of Lloyd's Mirror Must select "Setup: Lloyd's Mirror" from setup drop down menu
- Lloyd's Mirror Spectral Pattern Tyndall National Institute, Ireland