Year 5 – 6 | How Shadows Indicate the Sun’s Strength

Protecting My Skin full resource download  |  Concept 1: The sun and our skin download

Background

Students will conduct an experiment to observe how shadows appear at different times of the day. The aim of the activity is
to make connections between shadow length and the strength of ultraviolet (UV) radiation. Students will learn how shadow
lengths vary at different times of the day and indicate when the sun’s rays are most harmful.

Key messages

• The UV Index is an open-ended numerical scale that measures the amount of UV radiation reaching the earth’s surface.
• The UV Index describes the intensity of UV radiation
• The sun produces heat that we can feel and light that we can see. It also produces ultraviolet (UV) radiation that we
  cannot see or feel
• UV levels gradually increase from sunrise and peaks at solar noon on a clear sky day. Solar noon is the point at which the
  sun is directly overhead. UV levels then decline until sunset
• The lengths of shadows can determine when UV rays are most harmful. During early morning and late afternoon,
  shadows are longer. During the midday hours (10 a.m. to 3 p.m.), the sun is directly overhead, and shadows are shorter
  (or there is no shadow). UV rays are more intense and harmful at this time.

Resources

• Activity sheet: My Shadow Observations
• Metre rulers or measuring tape
• Yarn or string and tape for measuring shadows
• Sidewalk chalk
• www.myuv.com.au

Instructions

1. Activate prior knowledge and ask key questions to promote class discussion about UV and the sun.
2. Select the method students will use to measure their shadows.

• Rulers: Mark the place where students stand with chalk and have their partner mark the top of their shadow with
  chalk. Use rulers to measure the distance between chalk markings.
• String: Provide students with a long piece of string and two pieces of tape. The student creating the shadow will
  tape one end of the string where he/she is standing, while their partner will tape the string at the other end of the
  shadow. Measure the distance between tape marks.

3. Students complete the first five columns on the activity sheet and record their height.
4. Students measure their shadows and complete the shadow component of the activity sheet.
5. Review results and prompt class discussion to explain what they observed about shadows.
6. Students write a report to support their findings.
7. The report should include their observations and explanations with charts to support findings.

Key questions

• What do you know about UV and the sun?
• When is the sun’s UV radiation at its most harmful?
• What did you notice with your shadow at different times of the day?
• What did you learn from this experiment?

When completing activities and lessons outdoors when the UV Index is 3 or above, please remember to be SunSmart