Incandescent light bulbs use electrical energy to produce light energy, but it is not a direct transformation. Instead, the electrical energy is changed to a different form of energy, and then to light.

What form of energy does the "?" represent?

1. Sound

   No. Electrical energy can be transformed into sound energy, but that would not cause the bulb to light.

2. Thermal

   Yes. As electrical energy flows through the filament, resistance changes the electrical energy into thermal energy. When the filament gets hot enough, some of the thermal energy is converted into light.

3. Radiation

   No. The electrical energy is not transformed into radiation.

4. Friction

   No. The electrical energy is not transformed into friction.

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This is a photograph of the Painted Desert in Arizona. These layers of rock have not been folded or overturned, so we know that the layer on the bottom is the oldest. This is based on:

1. The Law of Superposition

   Yes! The Law of Superposition tells us that unless the layers have been disturbed, they will be in order of their age, with the youngest on the top, and the oldest on the bottom.

2. The Law of Crosscutting

   No. The Law of Crosscutting tells us that a feature (crack, fault, igneous intrusion, etc.) that cuts through a layer of rock is younger than the layer it cuts through. That makes sense, because the layer would have to be there first, before it could be broken by a fault, etc.

3. The Law of Relativity

   No. There is a theory of relativity, which deals with the basics of physics, not geology. There is no Law of Relativity.

4. The Law of Thermodynamics

   No. The Law of Thermodynamics deals with energy, not with layers of rock.

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