PHYSICS

• In both cases energy—measured in millions of electron volts (MeV)—is released because the products are more stable (have a higher binding energy) than the reactants.
• Fusion reactions are difficult to maintain because the nuclei repel each other, but fusion creates much less radioactive waste than does fission.
• If light strikes the boundary at an angle, the light is reflected at the same angle, similar to the way balls bounce when they hit the floor.
• In humans, hearing takes place whenever vibrations of frequencies from 15 hertz to about 20,000 hertz reach the inner ear.
• The sky is bright because molecules and particles in the air scatter sunlight.
• When light strikes a material, it interacts with the atoms in the material, and the corresponding effects depend on the frequency of the light and the atomic structure of the material.
• Reflection occurs when light hits the boundary between two materials.
• The prism bends, or refracts, light of different colors at different angles.
• Red light bends the least and violet light bends the most.
• This oscillation momentarily takes energy away from the light and then puts it back again.
• Refraction is the bending of light when it passes from one kind of material into another.
• Some of the light hitting the boundary will be reflected into the first material.
• Sound, physical phenomenon that stimulates the sense of hearing.
• Scientists have defined the speed of light in a vacuum to be exactly 299,792,458 meters per second (about 186,000 miles per second).
• In transparent materials, the electrons in the material oscillate, or vibrate, while the light is present.
• The light ray bends at an angle that depends on the difference between the speed of light in one substance and the next.
• Refract ion is the bending of a light ray as it passes from one substance to another.
• Such vibrations reach the inner ear when they are transmitted through air.
• Scattering occurs when the atoms of a transparent material are not smoothly distributed over distances greater than the length of a light wave, but are bunched up into lumps of molecules or particles.
• The hertz (Hz) is a unit of frequency equaling one vibration or cycle per second.
• The decibel scale is used primarily to compare sound intensities although it can be used to compare voltages.
• The speed of sound is different in other gases of greater or lesser density than air.
• The symbol for ohms is the Greek letter omega, Ω.
• Sound progresses through such gases more slowly.
• Quality is the characteristic of sound that allows the ear to distinguish between tones created by different instruments, even when the sound waves are identical in amplitude and frequency.
• The speed of sound in dry, sea level air at a temperature of 0°C (32°F) is 332 m/sec (1,088 ft/sec).
• The energy radiated by stars, including the Sun, arises from such fusion reactions deep in their interiors.
• Nuclear energy can be released in two different ways: fission, the splitting of a large nucleus, and fusion, the combining of two small nuclei.
• At temperatures above 15 million ° C (27 million ° F) existing there, hydrogen nuclei combine according to equation (1) and give rise to most of the energy released by the Sun.
• If the temperature is increased, for example, the speed of sound increases; thus, at 20°C (68°F), the speed of sound is 344 m/sec (1,129 ft/sec).
• Overtones are additional components in the wave that vibrate in simple multiples of the base frequency, causing differences in quality, or timbre.
• The speed of sound in air varies under different conditions.
• The molecules of some gases, such as carbon dioxide, are heavier and move less readily than molecules of air.
• The release of nuclear energy can occur at the low end of the binding energy curve through the fusion of two light nuclei into a heavier one.
• Electricians wear rubber gloves so that electric current will not pass from electrical equipment to their bodies.
• Another name for a voltage produced by a source of electric current is electromotive force.
• The relationship between current, voltage, and resistance is given by Ohm’s law.
• Resistance is measured in units called ohms.
• Electric current is measured in units called amperes (amp).
• The unit of electric charge, also named after Coulomb, is equal to the combined charges of 6.24 × 10^18 protons (or electrons).