Transcript Photosynthesis Pt 1 Light

Photosynthesis Part 1
The Electromagnetic Spectrum
•
Light as a wave
• Light travels in waves and its energy can
be measured in wavelengths.
• Short wavelengths are high energy
• Long wavelengths are low energy
Visible Light Spectrum
• White light or visible light is a blend of all
visible wavelengths
• This range is from 400 to about 800nm
• 1nanometer is 1 billionth of a meter!
When Light Interacts with matter
• 1. Light passes through the matter
(transparent)
• 2. Light is reflected (resulting in the colors
you see)
• 3. Light is absorbed (energy is released as
heat or used to excite electrons to make
chemical bonds!)
Light as a particle
• Although light travels in waves, it also behaves
as a particle.
• Light particles are called photons.
• Photons traveling in short wavelengths have
high energy.
• Photons traveling in long wavelengths have low
energy.
• When photons hit atoms, they can excite the
atom’s electrons or move them into a higher
energy state (Einstein –Photoelectric effect)
• These high energy electrons can then form
chemical bonds
Einstein and the Photoelectric Effect
• Albert Einstein won the
Nobel Prize for his work
on the Photoelectric
effect which showed that
light can behave as a
particle called a photon.
• These photons can excite
electrons to higher
energy levels allowing
them to form chemical
bonds to make, let’s say,
GLUCOSE!
Photosynthetic Pigments
• A pigment is a substance that absorbs
particular wavelengths of light.
• The colors that you see are the
wavelengths that are reflected, not
absorbed.
• If chlorophyll is a green pigment, then
what wavelength is not being absorbed?
• GREEN
Photosynthetic Pigments
• Chlorophyll: Two kinds – Chlorophyll A and
Chlorophyll B.
-Both Chlorophyll A and B absorb red and blue
wavelengths and reflect green
-Chlorophyll A is the primary photosynthetic
pigment – directly involved in converting sun
energy into chemical energy
-Chlorophyll B and other pigments absorb light
energy and transfer the energy to chlorophyll A.
Other Photosynthetic Pigments
• Carotenes: reflect orange wavelengths
• Xanthophylls: reflect yellow wavelengths
• These two pigments allow plants to use a
wider range of wavelengths than
chlorophyll alone.
• They are also what gives fall leaves their
various colors after the plant shuts down
chlorophyll production
Absorption Spectrum for Plant
Pigments
• Absorption spectrum: wavelengths
absorbed by a pigment