2. Photochemistry is the study of the interaction of
electromagnetic radiation with matter, resulting into a
physical change or into a chemical reaction.
OR
A process that start by light or start with light or initiated
by light.
4. One molecule is excited into an electronically excited state by
absorption of a photon, it can undergo a number of different
primary processes.
Photochemical processes are those in which the excited
species dissociates, isomerizes, rearranges, or react with
another molecule.
Photophysical processes include radiative transitions in which
the excited molecule emits light in the form of fluorescence or
phosphorescence and returns to the ground state, and
intramolecular non-radiative transitions in which some or all of
the energy of the absorbed photon is ultimately converted to
heat.
5. Luminescence
The glow produced in the
body by methods other
than action of heat i.e.
the production of cold
light is called
Luminescence.
Or Light from non-thermal
sources
There are three
types:
Luminal
and Hemoglobin , an
example of
chemiluminescence
6. 1.Chemiluminescence :
The emission of light
in chemical reaction
at ordinary
temperature is
called
chemiluminescence
e.g. The light
emitted by glow-
worms
A chemoluminescent
reaction in an Erlenmeyer
Flask
7. THERMOCHEMICAL RECATIONS PHOTOCHEMICALREACTIONS
These reactions involve absorption or
evolution of heat.
These reactions involve absorption of light.
They can take place even in absence
oflight i.e. dark.
The presence of light is the primary
requisite for thereaction to take place.
Temperature has significant effect
on the rate of
athermochemicalreaction.
Temperature has very little effect on the
rate of aphotochemicalreaction. Instead,
the intensity of light has a marked effect
on the rate of aphotochemicalreaction.
The free energy change ∆G of
athermochemicalreaction is always
negative.
The free energy change ∆G of
aphotochemicalreaction may not be
negative.
They are accelerated by the presence
of a catalyst.
Some of these are initiated by the
presence of a photosensitizer. However a
photosensitizer acts in a different way
than a catalyst.
Some Difference Between
