photoconductˈing or photoconducˈtive adjective

Relating to, or showing, photoconductivity

photoconductivˈity noun

The property of varying conductivity under the influence of light

photocurrˈent noun

An electric current produced by light

photodegraˈdable adjective

(of plastic) that will decompose after exposure to certain forms of light

photodiˈode noun

A two-electrode semiconductor device, used as an optical sensor

photodissociāˈtion noun (chem)

Dissociation produced by the absorption of radiant energy

photodynamˈic adjective

Relating to a treatment for cancer in which an introduced drug is activated by a laser beam

photoelasˈtic adjective

Relating to or exhibiting photoelasticity

photoelasticˈity noun

The property of certain solids of exhibiting optical changes due to compression or other stresses

photoelecˈtric adjective

Relating to photoelectricity, or to photoelectrons (photoelectric cell any device in which incidence of light of suitable frequency causes an alteration in electrical state, esp by photo-emission, eg in order to activate a switch, etc)

photoelectricˈity noun

The emission of electrons from the surface of certain materials by incidence of photons exceeding a certain energy

photoelecˈtrode noun

An electrode which can exhibit photoelectricity

photoelecˈtron noun

An electron released from a surface by a photon

photoelectronˈics singular noun

The science dealing with the interactions of matter and photons, esp those involving the emission of electrons

photo-emissˈion noun

The emission of electrons from the surface of a body after the incidence of photons

photofissˈion noun

Nuclear fission induced by gamma rays

phoˈtoflood or photoflood lamp noun

An incandescent lamp with a tungsten filament designed to run at a higher temperature but with a shorter life so that its emission spectrum more closely matches sunlight

photogen /fōˈtə-jən/ noun

1. (see -gen) a light-producing organ in animals
2. A light paraffin oil (also photogene)

phoˈtogene /-jēn/ noun

1. An after-image
2. A sensitive emulsion
3. A photograph (obsolete)

photogenic /-jenˈ or -jēnˈ/ adjective

1. Producing light
2. Produced by light
3. See also photogenic under photo-¹

photoionizāˈtion or photoionisāˈtion noun

Ionization produced by the action of electromagnetic radiation

photokinesis /-ki-nēˈsis or -kī-/ noun

(Gr kīnēsis movement) movement occurring in response to variations in light intensity

photoluminesceˈ intransitive verb

To produce photoluminescence

photoluminescˈence noun

Luminescence produced by exposure to photons

photoluminescˈent adjective

phoˈtolyse transitive verb

To cause photolysis in

intransitive verb

To undergo photolysis

photolysis /fō-tolˈi-sis/ noun

(see lysis) decomposition or dissociation of a molecule as the result of the absorption of radiation (chem)

photolytic /fō-tə-litˈik/ adjective

photomˈeter noun

An instrument for measuring luminous intensity, usu by comparing two sources of light

photometˈric adjective

photomˈetry noun

(the branch of physics dealing with) the measurement of luminous intensity

photomulˈtiplier noun

A photocell with a series of dynodes which amplify the emission current by electron multiplication

photonasˈtic /-nas-tik/ adjective

phoˈtonasty noun (Gr nastos close-pressed; biology)

A response in plants, etc to a change of intensity of light regardless of the direction of the light source

photonegˈative adjective

1. Tending to move away from light (biology)
2. Decreasing in conductivity when exposed to light (physics)

photopeˈriod noun

The period during every 24 hours when an organism is exposed to daylight

photoperiodˈic adjective

photoperiodicˈity noun

photopeˈriodism noun

The physiological and behavioural reactions of organisms to changes in the length of the daylight period

phoˈtophil adjective

1. (see -phil under phil-) light-loving
2. Turning towards the light

noun

An organism that seeks the light

photophilˈic adjective

photophilous /-tofˈ/ adjective

photophˈily noun

phōˈtophobe noun and adjective

photophoˈbia noun

(see phobia) a fear of or aversion to light

photophobic /-fōbˈik/ adjective

phoˈtophone noun

(Gr phōnē voice) an obsolete apparatus that transmits sound by converting it to a light signal and then back to sound at a remote receiver, analogous to a modern fibre optics system

photophonic /-fonˈik/ adjective

photophony /-tofˈə-ni/ noun

phoˈtophore /-fōr or -för/ noun (see -phore; zoology)

A luminiferous organ

photophoresis /-fə-rēˈsis/ noun

(Gr phorēsis a carrying) migration of suspended particles under the influence of light

photōpˈia noun

Vision in bright light, the eye's adjustment to daylight

photopˈic adjective

photopolarimˈeter noun

An instrument for measuring the polarization of light from planets or other distant objects

photopolˈymer noun

A light-sensitive polymer used in printing plates, microfilms, etc

photoposˈitive adjective

1. Tending to move towards light (biology)
2. Increasing in conductivity when exposed to light (physics)

photopsia /fō-topˈsi-ə/or photopsy /-topˈsi/ noun

(Gr opsis appearance) the appearance of flashes of light, owing to irritation of the retina

photorecepˈtor noun

A nerve-ending receiving light stimuli

photorefractˈive adjective

Of a material whose refractive index changes in response to light

photoresistˈ adjective

(of an organic material) that polymerizes on exposure to ultraviolet light and in that form resists attack by acids and solvents (also noun)

photosensˈitive adjective

Affected by light, visible or invisible

photosensitivˈity noun

photosensˈitize or photosensˈitise transitive verb

To make photosensitive by chemical or other means

photosensˈitizer or photosensˈitiser noun

phoˈtosphere noun

The luminous envelope of the sun's globe, the source of light

photospheric /-sferˈik/ adjective

photosynthesis /-sinˈthi-sis/ noun (botany)

The use of light energy to drive chemical reactions, most notably the reduction of carbon dioxide to carbohydrates by the green pigment chlorophyll

photosynˈthesize intransitive verb and transitive verb

photosynthetˈic adjective

phototacˈtic adjective

phototaxˈis noun (Gr taxis arrangement; biology)

Locomotory response or reaction of an organism or cell to the stimulus of light

phototelegˈraphy noun

Telegraphy by means of light (see also under photo-¹)

phototherapeutˈic adjective

phototherapy /fōˈtō-therˈə-pi/ or phototherapeutics /-pūˈtiks/ noun

(Gr therapeuein to tend) the treatment of disease by light

phototransistˈor noun

A transistor that amplifies current in response to light

phototrope /-trōp/ noun

A substance exhibiting phototropism

phototrophˈic adjective (biology)

Using light to generate energy needed to absorb nutrients

phototropic /-tropˈik/ adjective

phototropism /fōt-otˈrəp-izm/ noun

1. (see -trope) orientation in response to the stimulus of light (botany)
2. Reversible colour change on exposure to light (chem)

phototˈropy noun

Change of colour due to wavelength of incident light

phoˈtotube noun

An electron tube in which a cathode converts light into electric current

photovoltaic /-vol-tāˈik/ adjective

Producing an electromotive force across the junction between dissimilar materials when the junction is exposed to light or ultraviolet radiation, eg in a photovoltaic cell

photovoltaˈics singular noun

The science and technology of photovoltaic devices and substances