Phosphorescence and Fluorescence

Vanderbilt Student Volunteers for Science

Spring 2008

Training Presentation

Important!

• Please use this resource to reinforce your understanding of the lesson! Make sure you have read and understand the entire lesson prior to picking up the kit!

• We recommend that you work through the kit with your team prior to going into the classroom.

• This presentation does not contain the entire lesson—only selected experiments that may be difficult to visualize and/or understand.

I. Introduction • Ask the students to name some

objects that give off light, and whether they are hot or cold.

• Explain the difference between incandescence (hot light) and luminescence (cold light). Tell the students that today they will be working with two forms of luminescence.

• Explain the difference between phosphorescence (continues glowing after light is removed) and fluorescence (stops glowing after light is removed).– A good way to remember is

that the longer word (phosphorescence) glows for a longer time

I. Introduction (cont’d)• A. Demonstration of

Fluorescence – Show the students the paper towel

with an invisible drawing on it. – Shine the black light on the paper

to reveal the drawing (it was written with Chlorox II)

– Remove the light to show that the message is once again invisible.

– There is another message written on the purple paper that can be taken around to the groups at a later time.

• B. Demonstration of Phosphorescence

– Show the students the bead bracelet and ask what color the beads are (white).

– Shine the black light on the bracelet for 20 seconds and then ask again (different colors).

– Take the light away to show that the color takes time to fade.

• Distribute the boxes and goggles around the room.

• Tell the students to put their goggles on.

• Tell the students to take everything out of the box.

• Have them examine the laminated black paper with laundry detergent and zinc sulfide and record the color (s).

• Place it back into the box and expose it to the black light for 20 seconds. Record (on the board) any change in color they notice.

• Tell the students to remove the light, close the box lid, and look inside. Record the materials that continue to glow. Emphasize that the material is phosphorescing if it is glowing in the dark.

II. What Materials Fluoresce or Phosphoresce?

• Repeat this process with the neon paint, glow in the dark paint, and colored beads. Note also what happens to the label paper.

– Note: tell them to leave the beads in the bag.

II. What Materials Fluoresce or Phosphoresce contd.?

• Tell the students to take out a piece of paper towel and draw on it with the highlighter. Expose to the black light and observe what happens when the lid is closed.

• Repeat with the Clorox II and Q-tip.

II. What Materials Fluoresce or Phosphoresce contd.?

II. What Materials Fluoresce or Phosphoresce contd.?

• Distribute the minerals so each student can see the different types of fluorescing minerals.

• Shine the black light on it and record the color change.

• Collect all materials before going on to the next part. Please check that all the materials are accounted for.

III. What kind of light is needed to produce Fluorescence and

Phosphorescence?• Distribute a piece of

yellow vinyl and LED light to groups. Tell the students to gently “draw” a squiggle on the vinyl material using the LED lights in the order, BLUE, WHITE, RED. Point out that the side with the smiley face is the power button.

• Have the students record which LED’s made the material phosphoresce (the white and blue lights will).

III. What kind of light is needed to produce Fluorescence and Phosphorescence?

• Tell the students to look at the “rainbow on their instruction sheet.

• The high energy component of white light excites the materials. This is at the BLUE end of the visible light spectrum.– The high energy light, (blue and the white that contains blue light)

causes the vinyl to phosphoresce.– The red light does not have enough energy to cause the vinyl to

phosphoresce.

IV. Making Glow in the Dark Bracelets

• Collect all vinyl pieces and LEDs.

• Pass out beads and braid and have the students make a bracelet.– These bracelets are similar

to the ones made in the fall, except these beads will glow in the dark after being exposed to sunlight.

– Students may take their bracelets home.