photodiode

As nouns the difference between spectrometer and photodiode

is that spectrometer is (analytical chemistry) an optical instrument for measuring the absorption of light by chemical substances; typically it will plot a graph of absorption versus wavelength or frequency, and the patterns produced are used to identify the substances present, and their internal structure while photodiode is a semiconductor two-terminal component whose electrical characteristics are light-sensitive.

As a noun photodiode

is a semiconductor two-terminal component whose electrical characteristics are light-sensitive.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between photodiode and photoresistor

is that photodiode is a semiconductor two-terminal component whose electrical characteristics are light-sensitive while photoresistor is an electronic component whose resistance is inversely proportional to the intensity of incident light; a photoconductor.

As nouns the difference between diode and photodiode

is that diode is diode while photodiode is a semiconductor two-terminal component whose electrical characteristics are light-sensitive.