Physics
Biology
Absorbing Light Energy and Flourescent Light
Author
Cécile Bardel, Charles Baudelaire
Target Group
16-17 years old students
Brief Description
Absorbing Light Energy and Flourescent Light

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ABSORBING LIGHT ENERGY AND FLUORESCENT LIGHT

Topic handout (1/2)

Overview and research to carry out

When chlorophyll in a solution absorbs light energy, some electrons in its atoms absorb this energy. The effect of this is to put them in an

“excited state”. These electrons then return naturally to their initial state, giving back out the energy absorbed in the form of red light

(fluorescence). 

The aim is to show that the energy absorbed by the chlorophyll can be transferred to an electron acceptor. 
Resources

Diagrams representing the emission of fluorescent light after the chlorophyll absorb light energy 

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A pigment, such as chlorophyll, agitated by the light can come back to its initial state in one of two ways:

- by giving back out a reduced level of light (as fluorescent light) (diagram 1)

- by behaving as a reductor and giving away an electron to an electron acceptor (diagram 2)

Step 1: Come up with a plan to resolve the problem (10 minutes maximum)

Come up with a feasible plan which would allow you to show that the energy absorbed by the chlorophyll can be transferred to an electron

acceptor. 





ABSORBING LIGHT ENERGY AND FLUORESCENT LIGHT

Topic handout (2/2)


Step 2: Carry out the experiment to obtain exploitable data

Carry out the experiment on the agitation of chlorophyll in order to show that the energy absorbed by the chlorophyll can be transferred

to an electron acceptor. 

Step 3: Process the data and present your findings

In the form of your choice, process and present the raw data so that you have the necessary information to respond to the problem. 



Step 4: Used the obtained results to respond to the problem and answer the question

Process the results to show that the energy absorbed by the chlorophyll can be transferred to an electron acceptor





ABSORBING LIGHT ENERGY AND FLUORESCENT LIGHT

Experiment Protocol Handout


Equipment available and protocol for using the equipment  

Material :

 

-       Spinach leaves

-       Scales

-       Scissors

-       Beaker

-       Funnel, filter paper

-       Pestle and mortar

-       Sand

-       Pure ethanol

-       Solution containing the electron acceptor

-     Graduated test tube, beaker, translucent receptacles, pipette

-       UV lamp

   -    Paper towels

Procedure for the agitating of chlorophyll to show that the energy absorbed by the chlorophyll can be transferred to an electron acceptor.

 

-    Weight …100…..g of spinach leaves in a beaker and chop them roughly using a pair of scissors.

-       Place the chopped leaves in a mortar, and grind them with the sand and …3….. ml of ethanol.

-       Filter the ground solution into a beaker.

-       Divide up the filtrate into two receptacles.

-       Shine a UV lamp on the two receptacles and observe.

-       Add …1…..ml of a solution containing the electron acceptor into one of the two receptacles, and ……1.. ml distilled water in the other receptacle, then watch closely.

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 Using a UV lamp poses a carcinogenic risk to your health


  The electron conductor solution is toxic

 Ethanol is flammable

Handling precautions

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ABSORBING LIGHT ENERGY AND FLUORESCENT LIGHT

Lab sheet for the teacher


Materiel per experiment:

-       Spinach leaves (ensure that they are definitely green, don’t take young shoots of spinach)

-       Scales, scissors, kitchen paper

-       Beaker, filter, filter paper, pestle and morter, graduated test tube, beaker, spectophotromety tanks OR translucent glass receptacles, pipette

-       Sand (4g as a rough guide)

-       Pure ethanol

-       Solution containing the electron acceptor. "Hill’s solution" = Potassium ferricyanide. To prepare this reactant, dissolve 6.6g of Potassium ferricyanide in 100ml of distilled water.

   -    UV lamp (You can also use a similar powered lamp like an LED lamp or a projector as a substitute) 




ABSORBING LIGHT ENERGY AND FLUORESCENT LIGHT
Expected result



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Pure chlorophyll solution

Enlighted with UV
Chlorophyll solution with added electrons



Related files

Absorbing Light Energy and Flourescent Light 251 KB
expected result for the experiment 123 KB
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