Science Assessment

Students should know that:

1. Electromagnetic radiation is always given off by all objects. Some of this electromagnetic radiation transfers energy to objects that absorb it and some electromagnetic radiation is radiated into space.
2. Electromagnetic radiation transfers energy through space; it does not need a medium such as air or another object to transfer energy from one object to another.
3. Electromagnetic radiation is given off by objects in all directions [except from lasers and other specially designed light sources or when the radiation is reflected or blocked] and travels in straight lines; therefore energy can be transferred from an object by electromagnetic radiation in all directions to any object in the path of the electromagnetic radiation.
4. The temperature of an object affects the rate at which electromagnetic radiation is given off by the object.  The higher the temperature of an object, the more electromagnetic radiation the object gives off over a fixed period of time.
5. The surface area of the object absorbing the electromagnetic radiation affects the amount of energy transferred to it. The larger the surface, the more energy is transferred to the object over a fixed period of time.
6. The angle at which the electromagnetic radiation strikes an object affects the amount of energy transferred to it.  The closer the angle is to 90°, the more energy is transferred to the object over a fixed period of time.
7. Energy is transferred by radiation between objects in both directions. When there is more energy transferred from the first object to the second object than from the second to the first, there is a net transfer of energy from the first object to the second.  It is also possible that the same amount of energy is transferred by radiation in both directions, in which case there is no net transfer of energy between the objects.
8. Objects that absorb more energy by radiation than they give off get warmer, which means the thermal energy of the object increases.  Objects that give off more energy by radiation then they absorb get cooler, which means that the thermal energy of the object decreases (unless additional energy is supplied to the object (e.g. a lamp plugged into an electrical outlet)).  [This sub-idea assumes that neither object changes state, in which case the temperature of the object would not increase or decrease during the phase change.]

Boundaries:

1. Items do not ask students to calculate how much energy is transferred by radiation in a particular situation.
2. Items testing the idea that the temperature of an object affects the rate at which the object radiates electromagnetic radiation do not use contexts involving light bulbs of any kind.
3. Contexts of assessment items are limited to those that do not involve changes of state.
4. Students are not expected to know that the temperature of the object the radiation shines on increases asymptotically.  Items use time periods during which the temperature of the object noticeably increases the longer the radiation shines on the object.