Quick Answer:The Optical Needle | Parallax Pin is a steel sighting pin with a fine ground point, used on optical benches and with glass slabs and mirrors to trace light paths and locate images by the no-parallax method.
Last updated: 18 October 2026
Key Features
Fine, precision-ground needle point for sharp sighting.
High-contrast tip for easy sighting.
Used with optical benches, glass slabs and mirrors.
Finds image positions and focal lengths by the method of no parallax.
Technical Specifications
Specification
Value
Material
Steel
Point
Precision-ground needle point
Tip
High-contrast for sighting
How It Is Used
One pin serves as the object and a second is moved until it shows no parallax with the image seen in the mirror, lens or glass slab, meaning both are at the same place. The pin position is read from the bench scale or marked on paper, giving image distances for focal length work or the path of a ray.
Frequently Asked Questions
What is the Optical Needle | Parallax Pin used with?
Optical benches, glass slabs and mirrors, to trace the path of light and find focal lengths by the method of no parallax.
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