- In optics: a faint image caused by reflections at uncoated or antireflection-coated
surfaces. A prime example is the faint reflection from the uncoated
front surface of a rear-surface mirror. Using a front-surface mirror
eliminates the ghost image (but may cause other problems).
- In spectroscopy: a false image of a spectral
line caused by irregularities and imperfections in the ruling of
a diffraction grating.
AND OPTICAL PHENOMENA