EXPERIMENT 10.2

PURPOSE:

To investigate the properties of ultraviolet light and understand how it affects different materials.

BACKGROUND:

Ultraviolet (UV) light is a type of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays. UV light is invisible to the human eye, but it can cause certain materials to fluoresce (emit visible light). The sun emits UV radiation, which is partially blocked by the Earth's ozone layer. UV light is categorized into three types based on wavelength: UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm).

While UV light has beneficial uses like vitamin D production in our skin, sterilization, and forensic analysis, excessive exposure can be harmful, causing sunburn, premature aging, and increasing the risk of skin cancer. In this experiment, we will explore how UV light interacts with different materials and observe fluorescence.

MATERIALS:

• UV flashlight (blacklight)
• Various household items to test:
  • White paper
  • White cotton fabric
  • Laundry detergent
  • Tonic water
  • Highlighter markers
  • White/light-colored flowers
  • Petroleum jelly
  • Extra virgin olive oil
  • Banana (ripe and green)
• Sunscreen (SPF 30 or higher)
• Clear plastic or glass containers
• Darkened room

SAFETY PRECAUTIONS:

• Never look directly at a UV light source
• Limit exposure of skin to UV light
• Wear protective eyewear if available
• Keep UV light away from eyes

PROCEDURE:

1. Set up your experiment in a darkened room to better observe fluorescence effects.
2. Draw a design or write a message on white paper using a highlighter marker.
3. Let the ink dry completely, then observe the paper under normal light.
4. Turn off the lights and shine the UV flashlight on the paper. Record your observations.
5. Place a small amount of laundry detergent in a clear container and observe it under UV light. Record your observations.
6. Pour some tonic water into a clear container and observe it under UV light. Record your observations.
7. Apply a small amount of petroleum jelly on a piece of paper and observe it under UV light. Record your observations.
8. Pour a small amount of extra virgin olive oil into a clear container and observe it under UV light. Record your observations.
9. Examine both ripe and green bananas under UV light. Record your observations.
10. Apply a small amount of sunscreen to a piece of paper, leaving part of the paper uncovered. Shine the UV light on both areas and record your observations.
11. Examine white or light-colored flowers under UV light. Record your observations.
12. Test any other household items you're curious about and record your findings.

DATA:

ANALYSIS QUESTIONS:

1. What is fluorescence, and how does it relate to UV light?

2. Why do some materials fluoresce under UV light while others don't?

3. Based on your observations, how effective was the sunscreen at blocking UV light?

4. How might insects and other animals perceive flowers differently than humans, based on your UV light observations?

5. What are some practical applications of UV light in everyday life and various industries?

CONCLUSIONS:

Summarize what you learned about UV light and fluorescence. Discuss how different materials interact with UV light and why this is important in our daily lives. Include information about the protective role of sunscreen and the ozone layer against harmful UV radiation.