4.4a Different forms of electromagnetic energy have different wavelengths. Some exam-

ples of electromagnetic energy are microwaves, infrared light, visible light, ultraviolet

light, X-rays, and gamma rays.

4.4b Light passes through some materials, sometimes refracting in the process.

Materials absorb and reflect light, and may transmit light. To see an object, light from

that object, emitted by or reflected from it, must enter the eye.

4.4c Vibrations in materials set up wave-like disturbances that spread away from the

source. Sound waves are an example. Vibrational waves move at different speeds in

different materials. Sound cannot travel in a vacuum.

4.4d Electrical energy can be produced from a variety of energy sources and can be

transformed into almost any other form of energy.

4.4e Electrical circuits provide a means of transferring electrical energy.

4.4f Without touching them, material that has been electrically charged attracts

uncharged material, and may either attract or repel other charged material.

4.4g Without direct contact, a magnet attracts certain materials and either attracts or

repels other magnets. The attractive force of a magnet is greatest at its poles.