Question

A sunscreen manufacturer tests a new water-resistant sunscreen by finding 120 volunteers at a community pool. The subjects are randomly assigned to one of two groups by drawing either a 1 or 2 marked on slips of equal-sized paper from a bag. Half of the subjects use an old formulation, and half use the new formulation over an 8-hour time frame on the same sunny day. Test administrators apply a measured amount of sunscreen to each subject at the beginning of the day and reapply it at regular intervals throughout the day. Test subjects are asked to remain in unshaded areas as much as possible during the test. The levels of sunburn are compared at the end of the day.

Answer 1

The question pertains to Chemistry, as it focuses on testing the effectiveness of a sunscreen formulation based on its chemical properties and ability to protect skin from UVB and UVA rays.

Step-by-step explanation:

The experiment described aims to compare the efficacy of an old and new water-resistant sunscreen formulation. The study exposes volunteer subjects to UV radiation to evaluate sunburn levels, which is directly related to sunscreen performance. Given the context, it falls under the Chemistry subject, specifically the study of chemical compounds in sunscreens and their role in protecting the skin from ultraviolet rays.

It is essential to note that sunscreens are designed to protect against UVB and UVA radiation. Sun protection factor (SPF) is a measure of how well a sunscreen can protect the skin from UVB rays. A minimum of an SPF 30 is recommended, which suggests the product can block about 97% of UVB radiation. Even though going up to SPF 50 only increases UVB protection by 1%, it's vital to ensure the sunscreen also offers broad-spectrum protection against UVA rays.

In addition, while no sun protection products are genuinely waterproof, some are water-resistant. It is crucial for consumers to reapply these products every two hours, especially after swimming or sweating, to maintain effectiveness.