light beam vs irradiation

light beam and irradiation both are nouns.

Word	Noun	Adjective	Verb	Adverb
light beam	Yes	No	No	No
irradiation	Yes	No	No	No

As nouns, light beam and irradiation are synonyms defined as:

Other synonyms of light beam include beam, beam of light, ray, ray of light, shaft, shaft of light.

light beam (noun)	irradiation (noun)
a column of light (as from a beacon)	(medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance
	the apparent enlargement of a bright object when viewed against a dark background
	(Pavolvian conditioning) the elicitation of a conditioned response by stimulation similar but not identical to the original stimulus
	(physiology) the spread of sensory neural impulses in the cortex
	a column of light (as from a beacon)
	the condition of being exposed to radiation