Light Quality and Measurements

Question 1

What is the electromagnetic spectrum and what does it measure?

Answer 1

Streams of photons traveling in a wave-like pattern
Measures electromagnetic radiation

Question 2

How are visible light and photosynthetically active radiation (PAR) related?

Answer 2

PAR is a subset of visible light

Question 3

What are the differences between light quality, intensity, and distribution/quantity?

Answer 3

Quality: measure of usable light that is available for plant use
Intensity: brightness of light
Duration: how long the light is available

Question 4

What are the units of measurement for each ways of approaching light?

Answer 4

Lumens (brightness to human eye)
Lux (brightness in an area)
Watts (energy required to produce light)
PPF (measure of plant usable light per second)
PPFD (PPF measurement as it hits a surface)

Question 5

What types of light are best for horticultural production?

Answer 5

LED (most efficient, degrade over time)
Sodium (last a long time, produce heat)