Question

When two similar gratings are placed face to face with their lines parallel, there will appear a series of bands popularly known

Answer 1

Answer:

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Answer 2

Moire fringes

Explanation:

• When two similar gratings are placed face to face, with their lines parallel, a series of alternating light and dark bands referred to as moire fringes will appear.
• When one scale moves during a direction perpendicular to the lines with relation to a stationary index grating, the fringes are seen to maneuver at right angles to the motion.
• These fringes are largely free from harmonics. Two photocells within the viewing optics spaced 90 fringe-phase degrees apart are capable of generating bidirectional fringe counting signals.
• when repetitive patterns of semi transparent object are placed, moire patterns are formed. a small motion of 1 of the objects creates large-scale changes within the moiré pattern. These patterns will be wont to demonstrate wave interference.

When the gratings are placed face to face, the series formed is called as moire fringes.