SAT II物理考试常用术语汇总之Q-R.

　　SAT2考试时间为一小时，大部分为选择题，主要考察学生某一专业的知识，每科满分为800分，学生可以根据所申请的各专业和学校的要求参加。下面提供SAT2物理考试常用术语汇总的Q和R部分。

　　Q

　　Quark

　　The building blocks of all matter, quarks are the constituent parts of protons, neutrons, and mesons.

　　R

　　Radian

　　A unit for measuring angles; also called a “rad.” 2π rad = 360o.

　　Radiation

　　Heat transfer via electromagnetic waves.

　　Radioactive decay

　　The process by which unstable nuclei spontaneously release particles and/or energy so as to come to a more stable arrangement. The most common forms of radioactive decay are alpha decay, beta decay, and gamma decay.

　　Radioactivity

　　An object is called radioactive if it undergoes radioactive decay.

　　Radius of curvature

　　With spherical mirrors, the radius of the sphere of which the mirror is a part.

　　Raraction

　　An area of high air pressure that acts as the wave trough for sound waves. The spacing between successive raractions is the wavelength of sound, and the number of successive areas of raraction that arrive at the ear per second is the frequency, or pitch, of the sound.

　　Real image

　　An image created by a mirror or lens in such a way that light does actually come from where the image appears to be. If you place a screen in front of a real image, the image will be projected onto the screen.

　　Rlect

　　A wave on a string that is tied to a pole at one end will rlect back toward its source, producing a wave that is the mirror-image of the original and which travels in the opposite direction.

　　Rlected ray

　　The ray of light that is rlected from a mirror or other rlecting surface.

　　Rlection

　　The phenomenon of light bouncing off a surface, such as a mirror.

　　Rracted ray

　　The ray of light that is rracted through a surface into a different medium.

　　Rraction

　　The bending of light as it passes from one medium to another. Light rracts toward the normal when going from a less dense medium into a denser medium and away from the normal when going from a denser medium into a less dense medium.

　　Restoring force

　　The force that causes simple harmonic motion. The restoring force is always directed toward an object’s equilibrium position.

　　Right-hand rule

　　A means of dining the direction of the cross product vector. To dine the direction of the vector , position your right hand so that your fingers point in the direction of A, and then curl them around so that they point in the direction of B. The direction of your thumb shows the direction of the cross product vector.

　　Rigid body

　　An object that retains its overall shape, meaning that the particles that make up the rigid body stay in the same position relative to one another.

　　Rotational kinetic energy

　　The energy of a particle rotating around an axis.

　　Rotational motion

　　Occurs when every point in the rigid body moves in a circular path around a line called the axis of rotation.

　　Rutherford nuclear model

　　The model of the atom according to which negatively charged electrons orbit a positively charged nucleus. This model was developed by Ernest Rutherford in light of the results from his gold foil experiment.