Some of our everyday environments are constructed for us as buildings. This project has concentrated on buildings. Other environments have been “built” for us as clothing, appliances for cooking, cars, roadways, and bridges. Our environment is filled with technologies constructed for our convenience and comfort. Heat transfer is involved with how many of these things work. For example, some control devices in the home and at work depend on infrared heat transfer.
This short video (https://vimeo.com/63022456) shows a TV remote control pointed at a video camera. Cameras are more sensitive to infrared or heat radiation than the human eye. In the video, you see a little light flashing each time a button is pushed. That light is sending out infrared radiation. If you look at a TV remote while pushing buttons, you will not see this flashing light. Your eyes are not able to see infrared radiation on radiation in the so-called visible range or colors.
The activity can be conducted as an investigation, which can be started in the classroom and students can carry out at home.
Initiate discussion about TV remote controls. Students will be very familiar with how they are used but raise the question as to how the TV receives these signals. At this point there may be a student who has a correct or near correct response. Accept it along with others and suggest that we come back to visit these after conducting an investigation.
Guide the development of an question that can be investigated. For example, what are some of the characteristics of the signal generated by the TV remote?
What are some tests we could perform to investigate this signal?
Apparently the signal goes through air, will it go through other things? For example, will it transmit through, a single sheet of paper? Through water? Through clear glass? Through colored glass? How thick can the paper be? How thick can the glass be? Will it transmit through your finger? Through cloth? Etc.
This investigation can be partly done in class and more can be tried at home.
How wide is the signal? Can I point the remote at an angle to the TV? How big an angle? Lay the remote on a flat surface on a piece of paper and mark the angles tested. Determine how wide the sign is. Are there differences between remotes?
Will the signal bounce off of other objects and still get to the TV? Can you bounce the signal off the ceiling or the wall? Once you know how wide the signal is, point the remote at a wider angle but at a wall. Does the TV still turn on and off? Try bouncing it off of a piece of paper. Does the color matter? Can you bounce it off of clothing? What kinds of things will reflect a TV signal?
Have students gather systematic data from home and compare in class.
Next Generation Science Education Standards
Scientific and Engineering Practices:
– Asking questions (for science) and defining problems (for engineering)
– Constructing explanations (for science) and designing solutions (for engineering)
– Systems and system models
– Energy and matter: Flows, cycles, and conservation
- State some generalizations from the data generated from tests of several remotes.
- From the generalizations, what do you know about the signal from a TV remote? [For example, you know that the signal is similar to a flashlight. It reflects and it shines through some things and is block by others.]
- Why can’t you see any signal when you look at the remote? [You could play the video at this point or make one of your own.]
- What is the kind of signal that comes from a remote? [infrared or radiated heat]
- Why is infrared used in a remote control?