First-surface mirror
Videos
A first-surface mirror or front-surface mirror is a mirror with the reflective surface being above a backing, as opposed to the conventional, second-surface mirror with the reflective surface behind a
Example of a second-surface mirror (left) and a first-surface mirror (right). In both pictures, the pen is touching the surface of the mirror. "Ghosting" (a faint reflection from the first layer) is visible in the left image (more obvious when this file is displayed at full-size).
Technicians assemble 6 of the 18 first-surface mirrors used in the James Webb Space Telescope.
Thermal expansion
Videos
Thermal expansion is the tendency of matter to increase in size with increasing temperature. Matter generally increases in length, area, and volume, changing its size and density, in response to an in
Expansion joint in a road bridge used to avoid damage from thermal expansion.
Lord Kelvin, the namesake of the unit of measure
Thermal expansion of long continuous sections of rail tracks is the driving force for rail buckling. This phenomenon resulted in 190 train derailments during 1998–2002 in the US alone.
Drinking glass with fracture due to uneven thermal expansion after pouring of hot liquid into the otherwise cool glass