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Related Experiment Videos

The shadow rule: a simple method for sun protection

T F Downham1

  • 1Department of Dermatology, Henry Ford Hospital, Detroit, Mich, USA.

Southern Medical Journal
|July 22, 1998
PubMed
Summary
This summary is machine-generated.

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The shadow rule helps estimate sun angle and ultraviolet radiation (UVR) intensity. Shorter shadows indicate higher UVR, increasing sunburn risk, especially in middle latitudes.

Area of Science:

  • Environmental Science
  • Atmospheric Science
  • Dermatology

Background:

  • Solar altitude directly influences ultraviolet radiation (UVR) intensity.
  • Solar altitude varies with season and geographic location (latitude-longitude).
  • UVR exposure is a significant factor in skin health and sunburn.

Purpose of the Study:

  • To explain the shadow rule as a method for indirectly determining solar altitude.
  • To establish the relationship between shadow length, solar altitude, and UVR intensity.
  • To assess the risk of sunburn based on shadow length in middle latitudes.

Main Methods:

  • Utilizing the shadow rule: comparing shadow length to object height to determine solar altitude.
  • Applying trigonometry: the tangent of solar altitude relates object height to shadow length (tan alt = y/x).

Related Experiment Videos

  • Observing the inverse proportionality between UVR intensity and shadow length in middle latitudes.

    • Main Results:

    • A shadow equal in length to the object's height corresponds to a 45-degree solar altitude.
    • Shorter shadows indicate higher solar altitudes and thus higher UVR intensity.
    • In middle latitudes, shorter-than-person height shadows correlate with increased UVR intensity and sunburn likelihood.

    Conclusions:

    • The shadow rule provides a practical, indirect measure of solar altitude.
    • Shadow length is a useful indicator of current UVR intensity.
    • Awareness of shadow length can help individuals gauge sunburn risk and take protective measures.