Consider a leaf with a surface area of 2.5 cm2. On a sunny day it might receive sunlight with an average power per unit area of 350 W/m2. Of this incident light, only about 40% is useful for photosynthesis. (a) If the process was perfectly efficient (i.e. all the useful radiation was converted to stored internal energy), calculate the increase in internal energy of the leaf in a period of one hour. (b) In practice, the overall efficiency of the process (percentage of energy stored relative to the total incident energy reaching the surface of the leaf) is only about 6%. Discuss, in relation to the First Law of Thermodynamics, what happens to the remaining energy?
Humans are unable to convert radiant energy from the sun into stored energy that can be used
to do work. Plants, however, obtain their energy from photosynthesis – sunlight is used to
convert carbon dioxide and water into sugars (stored as an energy source) and oxygen.
Consider a leaf with a surface area of 2.5 cm2. On a sunny day it might receive sunlight with
an average power per unit area of 350 W/m2. Of this incident light, only about 40% is useful
for photosynthesis.
(a) If the process was perfectly efficient (i.e. all the useful
stored internal energy), calculate the increase in internal energy of the leaf in a
period of one hour.
(b) In practice, the overall efficiency of the process (percentage of energy stored
relative to the total incident energy reaching the surface of the leaf) is only about
6%. Discuss, in relation to the First Law of
remaining energy?
Given Information:
The leaf with a surface area (A) = 2.5 cm2
The sunlight with an average power per unit area (I) = 350 W/m2
The % of useful energy (ε) = 40%
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