20 terms

Historical Figures and Contemporary Physics

Galileo Galilei
(1564- 1642)
- The principle of inertia: the natural state of motion is uniform constant velocity
Isaac Newton
-Three laws of motion
1. An object in motion stays in motion unless action upon by an unbalanced force
2. ∑F= ma
3. Every action creates an equal but opposite reaction
-Law of gravity: F of gravity = Gm1m2/r²
James Watt
- Power: Developed the concept of power while wroking with steam enginees to improve their efficiency
Johann Kepler
- 1st law of planetery motion: Planetary motion is elliptical
- 2nd law of planetary motion: A line drawn from the central body to an orbiting body will sweep equal areas of space in euqal time intervals
- 3rd law of planetary motion: The time to take one orbit is proportional to the radius of the orbit, T² proportional to r³
Charles- Augustin de Coulomb
- Coulomb's law
Georg Simon Ohm
(1789- 1854)
Ohm's Law
V = IR
Michael Faraday
- Electromagnetic fields: Introduced a way to visualize electric and magnetic fields as lines extending through space
- Electromagnetic induction: emf = ∆∅/t
- discovered that an emf can be induced to stimulate the flow of a current in a loop of conducting material
- induced emf is a potential
- current created by changing the magnetic flux over time
Heinrich Lenz
Lenz's Law: dictates the direction of an induced current in a closed loop of conducting material, based on conservation of energy
James Clerk Maxwell
- Electromagnetic waves: Mathematically demonstrated that light is an electromagnetic wave moving at the speed of light
Thomas Young
- Young's double slit experiment: Shined monochomatic light through two narrow slits to create an interference pattern. The resulting pattern demonstrated that light is a wave phenomenon.
Christian Doppler
- Doppler effect: The shift in wavelength and frequency perceived in sound and light when the source is moving toward or away from an observer
Lord Kelvin
- Absolute zero: Developed the concept of absolute zero and its associated temperature scale. The units of temperature for this scare are named after him
James Joule
- Heat and work equivalence: Devised an experiment to show that the temperature of water could be increased y applying a flame or doing mechanical work on it. Showed that heat and work are both methods of adding energy to a system. This means that the energy associated with heat (calories) can simply be converted during the work.
Albert Michelson and Edward Morley
- Michelson-Morley experiment: Designed an elaborate device knownn as an interferometer to detect the motin of Earth through the invisible ether. The ether was believed to be the medium that allowed light to travel through space. The experiment failed to prove the existence of the ether and opened the door for new lines of thinking, such as Einstein's special theory of realtivity.
JJ Thomson
- Discovered the electron: While working with cathode rays passing through electric plates, he deduced the existence of the electron. He suggested that the atom is similar to a plum pudding, In this model, the atom is viewed as having an overall positive charge( pudding) and the negative electrons are distributed randomly (plumbs) throughout the atom
Max Planck
- Founder of quantum theory: While working with emitted light spectra, Planck suggested that light energy can be emitted only in multiples of specific quantities and are thus quantized. He derived a constant (Planck's constant) that determines the energy associated with the specific quantities he observed.
Albert Einstein
- Einstein's miracle year, 1905: Published four papers that changed physics. Three of these are addressed in introductory physics courses.
- Photoelectric effect: Suggested that light acts like a particle (photon) and that the energy of the photon is quantized. The energy of the photon can be calculated by multiplying Planck's constant by the frequency of the photon: E = hf
- Special relativity: All the laws of physics are the same in inertial frames. The speed of light in a vacuum is a constant 3e8 m/s regardless of the motion of the light source.
- Mass Energy Equivalence: Matter can be converted into energy and vice versa according to the equation: E = mc²
Ernest Rutherford
- Goil foil experiment: Fired alpha particles (positive helium nuclei without their electrons) at a very thin piece of fold foil. The scattering of the alpha particles revealed that the atom is mostly empty space consisting of a dense positive nucleus surrounded by orbiting electrons.
Niels Bohr
- Planetary model of the atom, including specific energy levels: Combining the concepts of his predecessors, mentioned above, Bohr deduced a model of the atom that explains why electron orbits do not decay and fall into the nucleus. His calculated energy levels, which electrons must occupy, math completely with the observations of light spectra emitted from these atoms.
the study of celestial objects