Lab Activity 9

Follow the procedures below to complete this Blocking UV Rays Lab to investigate the power of ultraviolet radiation. Read through the procedures first and answer question 1 before you complete the lab.

***You will submit this lab as part of Project 2, see Project 2 for further instructions. It is worth a total of 20 points. Complete this lab activity and save it with your course materials to submit later.


UV beads are sensitive to ultraviolet (UV) light and will change color when exposed to ultraviolet rays. Ultraviolet rays are a known carcinogen, and are frequently implicated in skin cancer. Your job is to evaluate the effectiveness of various substances at blocking UV radiation.


20 UV beads

1 oz. sunscreen (any SPF)

t-shirt (or a 3 x 3 piece of t-shirt material)


glass (such as an empty clear glass container)

4 oz. water in clear glass container like a drinking glass

watch or clock with a second hand


  1. Answer question 1 below before you begin the experiment.
  2. This experiment should be performed outside, in full sunlight. Find a location outside that will provide you with a work space. *Note – UV beads should not be exposed to UV light before the experiment, so keep them covered with a towel or some thick material.
  3. Establish a control by collecting 3 or 4 UV beads in your hand and exposing them to sunlight while timing how long it takes for the beads to change color (Note – these beads should not be reused for the experiment and placed off to the side). Record this in the data table provided below.
  4. Collect 3 or 4 UV new beads in your hand and hold one lens of the sunglasses over the beads. Next, expose them to sunlight making sure to keep the beads covered with the lens. Time how long it take for the beads to change color and then record this in your data table. Place the used UV beads off to the side so they are not reused.
  5. Repeat Step 3 for each of the other items, making sure to record the time in your data table.
    1. T-shirt – use only one thickness of the material
    2. Glass – place the glass so that it covers the beads
    3. Water – drop the beads into the water and then place it in the sunlight
    4. Sunscreen – put some sunscreen in your hand with the beads and move the beads around to cover them with the sunscreen. Perform this test last so the sunscreen on your hands do not skew the results of the other items (Extension – try different strengths of SPF sunscreen and record this data in the table by adding rows, then determine which SPF provides the most protection)


Before you begin the experiment, make sure that you have answered question 1. Then, collect and record your data in the following chart and answer question 2 below.

  1. Of the items listed above (t-shirt material, sunglasses, clear glass, water, and sunscreen), which item do you think will be most effective at blocking UV rays? Explain your reasoning. (5 pts)

Data Table (10 pts)

  1. Based on your data which item was most effective at blocking UV rays? (2 pts) Provide a scientific explanation as to why this substance was the most effective at blocking UV rays. (3 pts) You may need to do some online research to answer this question.
    1. Construct a pedigree based on the scenario from the lab using appropriate symbols and format as described in your textbook. (7 pts)

    1. In what ways do pedigrees simplify the analysis of inheritance? (7 pts)

    1. Using this lab as a frame of reference, how can you put into practical use your understanding of construction and analyzing human pedigrees? (6 pts)

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