Unit 3: Considering the Influence of Light and Thermal Phenomena on Local Weathe
Unit 3: Considering the Influence of Light and Thermal Phenomena on Local Weather
IV. Developing Additional Central Ideas Based on Evidence
A sunny day at the beach can be a lot of fun. Why does the sand get so hot, however, while the water is so cool when the sun has been shining on both the sand and the water in the same way for the same time? Sometimes the sky clouds over and a breeze comes up in the afternoon. Why does that happen? This section explores how light and thermal phenomena sometimes affect the local weather during a sunny day at the beach.
A. Exploring the effects of properties of materials
Question 3.7 What happens when light shines on sand and water?
Equipment: To explore the effects of various properties on what happens when light shines on sand and water, use:
- Lamp with bendable stem,
- Light probe connected to a computer with graphing software or cell phone app for reflectivity (LUX meter)
- Black paper, white paper
- Two identical clear cups
- Balance
- Sand and water at room temperature
- Two temperature probes, and a computer or two regular bulb and tube thermometers with a range from at least about 15°C to 35°C.
[In a remote learning situation, brown rice, split peas, or dried beans can serve as a substitute for sand if necessary. A simple balance can be made with a board (a ruler will do) and something on which to balance it like a playground teeter totter. Set this up so it is balanced and then use two identical clear cups to put about half a cup of water on one side and as much sand as you need to balance it on the other side. ]
- What properties of sand and water might affect what happens when light from the Sun shines in the same way for the same time on both the sand and the water?
- In the Before section of a physics notebook page, record your ideas and predictions about the effect of properties explored in units 1 and 2: reflectivity, thermal conductivity, and specific heat. How can you explore the effects of these properties of sand and water on what happens when sunlight shines on a beach?
- To explore the property of reflectivity, move a light probe connected to a computer or a cell phone with a LUX meter app over black and white paper as well as over sand and water. Does the angle of reflection seem to matter?
- One way to explore differences in thermal conductivity and specific heat is to use equal amounts of the materials. Should one use equal amounts by mass or by volume?
- The property of specific heat is expressed in terms of the number of calories needed to change the temperature of one unit of mass by one degree Celsius so equal amounts by mass seem appropriate. Use a balance and identical clear cups to measure equal masses of sand and water at room temperature. Compare the volumes of the equal masses of sand and the water in the cups. What does this imply about the density of sand compared to the density of water?
- Set up a lamp with curved stem shining from the same distance away on cups with equal