Transcript Lighting - Science at NESS

Lighting
Types of Lighting
Natural light: Light that is emitted from electrical
or chemical reactions that occur in nature
Eg. Sunlight, Moonlight
Artificial Light: Man made. Made by electricity
or chemical reactions
Eg. Light bulbs
Light and its Wavelengths
Wavelengths: Light consists of a mixture of
different color.
Colors are created based on the wavelength
Plants and Lighting
Photosynthesis: The process used by plants to make
sugar. Sugar is made from joined carbon molecules.
Plants need light energy to break apart CO2 and
make sugar.
Photosynthesis and Wavelengths:
-Violet, blue, orange and red is absorbed = used for
photosynthesis.
-Green is reflected back = do not absorb that light
for energy
How do Plants Capture Light energy
Pigment Molecules: Special molecules used by
plants to transform light energy into chemical
energy. Found in the chloroplasts of cells.
Pigment Molecules:
Chlorophyll A
Chlorophyll B
Carotenoids
Wavelengths used by Plants
Types of Artificial Light
Incandescent
Incandescent light: Light created through a
tungsten wire as electrons are squeezed through
it. Give off redish yellow light.
Life expectancy: 750hrs
Incandescent
Pros: Does not require a ballast.
Inexpensive to buy. Does not contain
harmful chemicals
Cons: Has a short life expectancy,
Inefficient, produces more heat then
light. Consumes large amounts of energy
Metal Halides
Metal Halides: Contain mercury
and metal halides (metal +
bromide, iodide) in gas form.
Gives off blue spectrum light.
Belongs to the HID group of light
Lifespan: 8000hrs
Uses: Blue light stimulates
vegetative growth (leaves) such as
lettuce, cabage and swiss chard
HID: High intensity discharge
Metal Halides
Pros: High light output
compared to incandescent. Blue
light is useful for foliage. Cons:
Low levels of red spectrum light
leads to poor flowering.
Produces lots of heat.
Expensive to buy and use.
Contains mercury.
Fluorescent
Fluorescent: low pressure mercury vapor gas bulb. Gives off
blue or red spectrum light.
How does it work?
1) Electric current gives the energy needed to activate the
mercury
2) This causes it to give off ultra violet light energy.
3) The ultra violet light will intern provide energy needed for
the phosphorous coating inside the bulb to light up.
Uses: Used for seedlings.
Larger bulb for adult plants
Lifespan: 20,000 hours
Fluorescent
Pros: Low heat production. Can be placed close
to plants. Efficient electricity use. Wide range of
wavelengths. Long life.
Cons: Contains mercury. Requires a ballast to
control current (ballast replacement if
expensive)
High-pressure Sodium
High Pressure Sodium (HPS): Contain
sodium Gives off large amounts of red
light as well as other wavelengths
Uses: red stimulates flowering.
Increased flowering leads to increased
fruit production (tomatoes, peppers,
cucumber squash etc.)
Life span: 15 000 hrs
Low blue light results in long thin
green growth = HPS are often used as
supplemental light in greenhouses or
indoors with metal halide.
High-pressure Sodium
Pros: Gives off large amounts of
red which makes it ideal for
flowering. Produces bright light.
Cons: Produces high amounts of
heat. Low production of blue
light means it will need to be
combined with blue wavelength
light. Uses a lot of electricity.
LED
LED (light emitting diode): Light produced by
electrical current. Wavelengths produced depend
on the LED. All visible wavelengths are available.
Ratio of blue to red is 6:100.
Lifespan: 50,000hrs
Uses: Growing plants indoors.
Use depends on the ratio of
blue:red light.
High b:r ratio = Grow foliage
Low b:r ratio = Fruit and
flowering
LED
Pros: Set the light to the requirements of the
needs of the plants. Low electricity use. Low
heat production. Long lifespan
Cons:
New technology
= Expensive to buy.
= Unexpected breakdowns
Summary table: Pros and cons