Light is Vital for Photosynthesis

Generally speaking, there are cells within the ‘eye’ that exist only to capture light, hence the human term, ‘visible light spectrum’.  Plants are multicellular autotrophs with cell walls made of cellulose.  Autotrophs make their own food and accomplish this through the photosynthesis.

Light spectrum provides plants with information about the environment for germination, to grow certain shapes, sizes or colours, and to protect themselves, (with angiosperms) when they flower or fruit. Plant species vary in behaviour and are not all that different from one another but generally they all proceed to grow and form from the light source’s quality, intensity, duration and direction.

Light is vital for photosynthesis, and it is necessary to direct plants growth and development.  Light acts as a signal to initiate and regulate photoperiodism and photomorphogenesis.  Light waves have crests and valleys of a particular height or amplitude. This parameter of waves is perceived as brightness or intensity.

The general areas which plants receive optimal levels of light are in the ranges from 400700 nm which is called Photosynthetically Active Radiation (PAR).  PAR is a measurement of quantum units, when considered as a wave; light has a wavelength and a frequency.

Light as a Wavelength

Light is Vital for Photosynthesis

Highest Energy ⇔ Lowest Energy


Spectroscopy or spectrum pertains to the dispersion of an object’s light into its component colors (i.e. energies).  There are a range of units for this parameter, both English and Metric depending on the source, the surface, or the passage.  Light can also be thought of as a stream of particles, photons, or quanta.  In this case, units can be expressed in moles per square meter per second (mol m–2 s–1), where “moles” refers to the number of photons (1 mol of light = 6.02 × 1023 photons, Avogadro’s number).  This measure is called photon.  It is used commonly to describe PAR in the range of 400-700 nanometres (nm) wavebands.



Light as a Frequency

Light as a Frequency (click)

Think of one of your experiences on one of the various Great Lakes or the ocean, all of them have waves.  Waves are disturbances, ripples on the water, and they possess a certain height
(amplitude), with a certain number of waves rushing past you every minute (the frequency) and all moving at a characteristic speed across the water (the wave speed).  Notice the distance between successive waves? That’s called the wavelength.  If we assume that the waves are successive or intermittent, we can find a pattern and quite literally speculate at the miracles that are unfolding right in front of our eyes in the visible light spectrum.

Visible waves have great utility for the remote sensing of vegetation and for the identification of different objects by their visible colors.

Depositphotos_14444279_xl Electromagnetic spectrum Infographic

Electromagnetic Spectrum (Frequencies and Wavelengths)

You can see from the electromagnetic spectrum infographic that we can observe the telescoping nature of wavelengths shorter than visible light include gamma rays, x-rays, and ultraviolet light spectrum areas, they are measured in units of nanometers (nm for short).  Infrared is also measured in units of nm when looking at the lower portion of the frequency/spectrum or wavelength of a photon.  When we observe the higher frequency or wavelength of a photon it starts to lengthen, thus, we measure it in (cm).  Then we continue onward toward Radio Waves in ascending order from radar, TV-television, FM-frequency modulation (approx 3 m) and AM-amplitude modulation we measure it in meters.

Electromagnetic radiation spans an enormous range of frequencies or wavelengths, as is shown by the electromagnetic spectrum. Customarily, it is designated by fields, waves, and particles in increasing magnitude of frequencies–radio waves, microwaves, infrared rays, visible light, ultraviolet light, X rays, and gamma rays. The corresponding wavelengths are inversely proportional, and both the frequency and wavelength scales are logarithmic which is a nonlinear scale used when there is a large range of quantities.

The common uses include the earthquake strength, sound loudness, light intensity, and potential hydrogen (pH) of solutions.

The electromagnetic spectrum vector diagram

The Electromagnetic Spectrum

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The “electromagnetic spectrum” of an object has a different meaning, and is instead the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.

The electromagnetic spectrum extends from below the low frequencies used for modern radio communication to gamma radiation at the short-wavelength (high-frequency) end, thereby covering wavelengths from thousands of kilometers down to a fraction of the size of an atom.

Fun Fact

Ultra-high-energy gamma rays are gamma rays with energies higher than 100 TeV (0.1 PeV). They have a frequency higher than 2.41×1028 Hz and a wavelength shorter than 1.2×10−20 m. As of 2014, they are theoretical only and have not been detected. The highest energy astronomically sourced gamma rays detected are very-high-energy gamma rays. It is conceivable that the limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length.  Until the middle of last century, it was believed by most physicists that this spectrum was infinite and continuous.

Mathematical Fun

What wavelength carries more energy, 400nm or 700 nm?  A photon at 400 nm, which is in the blue region of the spectrum, has twice the energy of a photon at 800 nm, from the red & infrared region of the spectrum. (400nm-800nm is used in reference to simplify the example of the mathematics).

A photon of 400 nm light contains 4.97 × 10–19. On the other hand, the 800 nm photon contains 2.48 × 10-19. The higher the wavelength of a photon, the lower its energy is and on the opposite end of the spectrum, the lower the wavelength of a photon the higher its energy is.  In other words, red has the longest wavelengths and carries the least amount of energy and blue has the shortest wavelength and carries the most amount of energy (in the visible light spectrum).