relative refractive index
dišan-e šekasti-ye bâzâni
Fr.: indice de réfraction relatif
The ratio of the sine of the angle of incidence to the sine of the angle of refraction for a ray passing out of one of the media into the other.
Fr.: réfracteur de Yerkes
The largest → refracting telescope and the last of the great refractors with a lens diameter of 102 cm (f/d = 19), completed in 1897. The lens was ground by American telescope builders Alvan Clark & Sons. Used mainly for both visual and photographic studies of double stars, it is typical of the long-tube refractors traditionally employed in such work.
After Yerkes Observatory; → refractor.