pho·to·ac·tive 
(fō′tō-ăktĭv)
(fō′tō-ăktĭv)adj.
1. Capable of responding to light photoelectrically.
2. Capable of responding to sunlight or ultraviolet radiation by chemical reaction.
pho′to·ac·tivi·ty n.
- up-tempo
- uptempo
- up the creek (without a paddle)
- up the river
- up the spout
- up the wall
- up the wazoo
- up the wind
- upthrow
- upthrust
- uptick
- uptight
- uptightness
- uptime
- up to
- up to date
- up-to-date
- up-to-dateness
- up to ears
- Upton Beall
- up to neck
- up to (one's) ears
- up to one's ears
- up to (one's) neck
- up to one's neck