Sensing the Light: Teacher Instructions

Grade Level: K-5 (modify for K-1 as a guided demonstration and discussion)

Learning Goal

Students explore different ways light can be detected by comparing:

• Brightness sensing (how much light is present)
• UV sensing (detecting a specific type of light)

Students use their eyes, UV test cards, and UV-reactive beads to investigate how different sensors respond to light.

Materials

For a class of about 10 students:

• UV flashlight (black light)
• UV-reactive beads
• UV test cards/paper
• String or pipe cleaners (1 per student)
• Sunscreen
• 2 plastic sheet protectors or clear plastic bags per group
• Pencils
• Colored pencils or crayons
• Whiteboard or chart paper

Before Class

Prepare Sunscreen Shield

1. Leave one sheet protector/bag untreated.
2. Apply a thick layer of sunscreen to part of the second sheet protector/bag.
3. Test it with a UV bead and flashlight.
4. The sunscreen-covered protector should block most or all of the UV light so the bead does not glow or change color noticeably.

Decide on Location

• Outdoors works best.
• If going outside is not possible, use a window and/or the UV flashlight indoors.

For Grades K-1

Plan to lead the activity as a whole-group demonstration rather than having students complete worksheets independently.

Activity Procedure

1. Finding Bright and Dark Areas (5 minutes)

Tell students they will be investigating how sensors detect light.

If possible:

1. Take students outside.
2. Ask them to find:
   • The brightest spot they can see
   • The darkest/shadiest spot they can find
3. Discuss:
   • What sensor did they use? (Their eyes)
   • What signal were they detecting? (Light)

Return to the classroom.

Note: This can also be done indoors by comparing well-lit and dim areas.

2. Discuss Different Types of Light Sensing (5 minutes)

Explain that sensors can detect light in different ways:

• Brightness sensors measure how much light is present.
• Color or wavelength sensors detect specific types of light.

Ask:

When you looked for the brightest spot, what kind of sensing were you doing?

Guide students to the idea that their eyes were acting as brightness sensors.

3. Introduce UV Light (5 minutes)

Explain:

• Sunlight contains many colors or wavelengths of light.
• Some wavelengths are invisible to our eyes.
• One invisible type is ultraviolet (UV) light.
• Too much UV light can damage skin and cause sunburns.

Show the UV flashlight.

Ask whether students have seen similar lights before, such as:

• Black lights
• Reptile habitats
• Nail salons

Safety Reminder: Never shine the UV flashlight into anyone’s eyes.

4. Measure UV Light with Test Cards (5-10 minutes)

Give each group a UV test card.

1. Have students test UV levels in:
   • The brightest location
   • The darkest location (optional)
2. Record the results on the board.

Discuss:

• Did all locations have the same amount of UV light?
• Which locations had the highest readings?

5. Compare UV Sources (5 minutes)

Shine the UV flashlight directly onto a UV test card.

Ask students:

Which source produced the highest UV reading?

Students should observe that the flashlight produces a stronger response than the locations they tested.

6. Explore UV Beads (5-10 minutes)

Give each student:

• A pipe cleaner or string
• Several UV beads

Have students make a bracelet.

Then:

• Take bracelets outside or
• Use the UV flashlight indoors

Students should observe the beads changing color or glowing.

Afterward, ask students to:

• Draw what they saw
• Describe what happened to the beads

For K-1, discuss observations as a group.

7. Demonstrate How Sunscreen Blocks UV Light (10 minutes)

Dim the room lights.

Test 1: No Sunscreen

1. Place UV beads under the untreated plastic protector.
2. Shine the UV flashlight on the protector.
3. Students should see the beads glow or change color.

Test 2: With Sunscreen

1. Place UV beads under the sunscreen-coated protector.
2. Shine the flashlight again.
3. Students should notice much less color change or glow.

Discuss:

• What was different between the two tests?
• What do you think the sunscreen is doing?

Explain:

Sunscreen blocks or absorbs UV light before it reaches our skin, similar to how it prevented UV light from reaching the beads.

Wrap-Up Discussion (5 minutes)

Review the key ideas:

• Our eyes can detect brightness.
• Some sensors detect specific wavelengths of light.
• UV beads and UV cards respond to UV light.
• Sunscreen helps block UV light.

Ask:

• When might UV beads be useful?
• When might UV test cards be useful?

Possible answers:

• UV bead bracelets can remind people to reapply sunscreen.
• UV test cards can measure UV levels outdoors or in reptile habitats.

Cleanup

• Collect UV flashlights.
• Collect UV test cards (they can be reused many times).
• Save any unused UV beads and pipe cleaners.
• Discard used sunscreen-covered bags or sheet protectors if desired.

Students may take their UV bead bracelets home to continue exploring how UV light changes the beads in different environments.