such as "Introduction", "Conclusion"..etc
The energy produced by the sun reaches the earth as
electromagnetic radiation. Light and other forms of electromagnetic radiation
are considered to have both a wave nature and a particle nature. Particles or packets of
light (its particle nature) are known as photons - the smallest divisible units of light.
The brightness of light depends on the number of photons absorbed per unit
time. Each photon carries a fixed amount of energy which determines the amount
that the photon vibrates. The distance moved by a photon during one of it
vibrations is referred to as its wavelength and is measured in nanometres.
Electromagnetic radiation spans a broad range of
wavelengths. At the one end of the spectrum of electromagnetic radiation
there are gamma rays which have a wavelength of 10-5 nm and at the
other end, radio waves which have a wavelength of 1012nm. A
very small part of this spectrum can be seen by the human eye i.e. between the
wavelengths 380 and 750 nm. This part of the electromagnetic spectrum is called
Almost all life depends ultimately on this part of the spectrum for its energy.
Humans perceive the different wavelengths of visible light as different
Within the spectrum the longer the wavelength of the
radiation, the slower the vibration of the photons and the less energy each
photon contains. Thus photons of ultraviolet light, at the blue end of the
visible spectrum, have shorter wavelengths and contain more energy than red
light and infrared radiation.
Chlorophyll does not absorb all the wavelengths of visible
light equally. Chlorophyll a,
the most important light-absorbing pigment in plants, does not absorb light in
the green part of the spectrum. Light in this range of wavelengths is reflected.
This is the reason why chlorophyll is green and also why plants (which contain
a lot of chlorophyll) are also green.
To limit the inaccuracy of the experiment, it was important
to use a constant time (1 min) for each time the experiment was done. The lamp
stayed the same distance from the beaker and the same plant each time and the coloured
paper sheets were all the same size. The experiment was repeated two times and
the results were averaged to ensure that they were accurate.
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