An instrument for measuring the intensity of light; a photometer.

Any of various instruments for measuring the intensity of light, or for comparing the intensities of light from different sources.

A measurer of transparency; spec. an instrument for measuring the transparency of the atmosphere.

An instrument for measuring the intensity of light; a photometer.

An instrument for measuring the refractive index of a substance.

an instrument for directly determining the refractive index of a small sample of a liquid.

An instrument for measuring variations in atmospheric refraction, usually consisting of a telescope having additional lenses or mirrors which bring…

In full total reflectometer. An instrument for determining the refractive index of a transparent solid (or liquid) by measuring the critical angle…

an instrument for measuring very weak infrared or microwave radiation.

an apparatus for measuring the whole light emitted from a source.

an instrument for measuring the relative intensities of light from two different sources, esp. sources of different colours, by measuring the…

An instrument for making photometric measurements of very small areas.

An instrument for measuring diffraction, esp. one used to study crystalline materials and their atomic structure by measuring the diffraction of…

a photometer that measures the intensity of light received within a cone of small angle, typically 2° or less.

Astronomy. A telescopic apparatus for measuring the polarization of light from celestial objects; a polarimeter combined with a photometer.