Online Physics Glossary 
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Word 
Meaning 
Remarks 
Principal axis 
Line connecting center of curvature of spherical mirror with its geometric vertex. Line perpendicular to plane of lens passing through its center.


Principle of superposition 
Displacement due to two or more forces is equal to vector sum of forces.


Projectiles 
Motion of objects given initial velocity that then move only under force of gravity.


Proton 
Subatomic particle with positive charge that is nucleus of hydrogen atom.


Quantized 
A quantity that cannot be divided into smaller increments forever, for which there exists a minimum, quantum increment.


Quantum mechanic 
Study of properties of matter using its wave properties.


Quantum model of atom 
Atomic model in which only probability of locating electron is known.


Quantum number 
Integer ratio of energy to its quantum increment.


Quark 
Basic building block of protons, neutrons, other baryons, and mesons.


Quark model 
Model in which all particles that interact via the strong interaction are composed of two or three quarks.


Radiation 
Electromagnetic waves that carry energy.


Radioactive decay 
Spontaneous change of unstable nuclei into other nuclei.


Radioactive materials 
Materials that undergo radioactive decay.


Range of projectile 
Horizontal distance between launch point of projectile and where it returns to launch height.


Ray model of light 
Light may be represented by straight line along direction of motion.



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