Infrared waves are useful and critical in fields of communication, science, military and business. The infrared radiation is versatile and cannot be seen by the human eye. The infrared light waves have longer wavelengths than the ultraviolet and the visible white light have. The infrared waves emit heat even in the absence of direct sunlight. The IR rays can pass through opaque objects, such as metal, black plastic and even dark clouds, due to its longer wavelengths. However, the infrared radiation (IR) is also dangerous.
Infrared radiation (IR) is useful in detector technology and security systems by the police, military or health sector, and forest surveillance and astronomy.
The assigned experiment involves the use of infrared radiation with the source of radiation (the student will use a television and stereo to enhance reliability of the results) and the remote control as an infrared light source. The television and stereo have built-in IR detectors that can sense infrared light. The IR signals respond to the television and stereo, according to respective wavelengths. The universal remote control responds to different infrared wavelengths. This way, the signals can control different equipment.
The study determines the transparency of various objects to infrared light using a television remote control. The remote control works well when it is aiming at the TV or stereo. Different objects, as listed in the table, respond differently to the remote control, allowing the student to determine the transparency and reflection of infrared light. The materials vary in visible transparency, surface, color, thickness and density. Under diverse arrangements of these materials, the student observed that infrared light reflects from different positions in a room. Similarly, opaque objects either absorb or reflect IR light.
In the final steps of the experiment, the student varies the positions and adds more items to verify results. This way, the student will not draw false conclusions from observations of the experiment. The results are as presented on the Infrared Lab Data Sheet below.
Question One: Materials that are Transparent or Opaque to IR light
From the study, one can infer that thin plastic and clear polythene paper pass a considerable amount of infrared light. However, different materials made of thin plastic do not absorb or reflect the IR light. As a result, the remote control works when the object is put on the path of the IR light. An observation indicates that when the remote is further from the TV or stereo, response is not easily achieved. The distance from the television also affects the effectiveness of infrared light. It was observed that when closer to the device, the remote control still works even when obstructed by the hand (flesh).
The objects transparent to infrared light have low density and are not necessarily visibly transparent. Similarly, thicker objects did not allow passing through of infrared light as it was absorbed by objects. In addition, shiny objects also reflected the IR light.
The objects opaque to infrared light have high density. They absorb the infrared rays rather than letting them pass through them. Also, most of the opaque objects that do not absorb the infrared light reflect it to the room, for instance the white cotton T-shirt, dark plastic, rubber, mirror, carton box paper and mirror. Thick objects, even though with low density, are also opaque to infrared light, as in case of the stuffed animal and pillow. However, they reflect the infrared light. The fingertip is totally opaque to infrared light.
Question Two: Materials that reflect IR light
Some thick materials, such as pillows and stuffed animals, are characterized with low density. They reflect the IR light; however, do not allow rays to pass through. Similarly, other materials, such as the white cotton T-shirt, dark plastic, rubber, mirror, carton box paper and mirror also reflect infrared light. A common characteristic of all the materials is their low or medium densities that do not allow the total absorption of light