Notes, summaries, assignments, exams, and problems for Physics

LASER = Light Amplification by Stimulated Emission of Radiation

A laser is actually an oscillator rather than a simple amplifier. The difference is that an oscillator has positive feedback in addition to the amplifier.

Light is understood in a general sense: electromagnetic radiation with a wavelength around 1 μm. Thus, one can have infrared, visible, or ultraviolet lasers.

The atomic medium with population inversion used in the laser is called the active medium. The positive optical feedback is obtained by placing the active medium between two mirrors. One of them (M1) totally reflects back the light (R1 = 1) to the active medium, while the other one (M2, called the output coupler) has a reflectivity less than unity (R2 < 1) and allows some... Continue reading "Introduction to LASER Technology: Types, Operation, and Applications" »

DEFINITIONS

DISTANCE

How much ground an object has covered/traveled.

DISPLACEMENT

The change in position of an object.

SCALAR QUANTITY

Quantity that only has magnitude and no direction.

VECTOR

Physical quantity that has both magnitude and direction.

CONSTANT SPEED

Speed that does not change.

VELOCITY

Speed in a given direction.

FRAME OF REFERENCE

A background used to judge motion/speed (precise location of an object).

INSTANTANEOUS SPEED

Speed at a given moment.

ENERGY

The capacity/power to do work/move an object by applying force.

MATTER

Anything that has mass and takes up space (how much matter).

WEIGHT

Measure of how gravity pulls matter.

SPEED

Amount of distance traveled in a certain amount of time.

AVERAGE SPEED

Total distance divided by total time.

TIME DISTANCE

Application of Atomic Structure to Static Electricity

• All material objects are composed of atoms.
• An atom consists of a nucleus and a vast region of space outside the nucleus.
• The nucleus of the atom contains positively charged protons and neutral neutrons.

Charging by Friction

The frictional charging process results in a transfer of electrons between the two objects which are rubbed together.

Triboelectric Series: materiales ordenados según la capacidad de tendencia de atraer electrones.

Electrizar: cargar una sustancia/cuerpo que era neutra.

Charging by Induction

Is a method used to charge an object without actually touching the object to any other charged object.

The Electroscope

An electroscope is a device which is capable of detecting the presence... Continue reading "Static Electricity and Fundamental Electric Principles" »

Understanding Waves and Energy Transfer

A wave is a disturbance that travels a distance, carrying the energy which generated it. When the wave travels through a medium, like water or air, it does not displace the particles of the medium.

Characteristics of a Wave

• Wavelength: This is defined as the distance between two adjacent peaks or troughs of the wave. It is expressed in metres (m).
• Frequency: This is the number of oscillations or complete movements that a wave produces in one second. Its unit in SI is the Hertz (Hz).
• Speed of Propagation: This is the distance, e, that the wave travels divided by the time taken, t. It is expressed in m/s.

  Waves travel at a constant speed. Therefore:

  V_wave = e/t

  Which implies:

  e = V_wave · t

• Amplitude: This is the

Human Evolution: From *Orrorin* to *Homo Sapiens*

The Earth was formed 4,500 million years ago. There is evidence that the hominid family emerged 6 million years ago, with our species, Homo sapiens sapiens, appearing only 150,000 years ago. Our species is characterized by the development of the brain, which allows for complex social behavior, consciousness of our own existence, and a great capacity for communication. The evolution of our species includes the following:

Key Hominid Species

1. Orrorin tugenensis: Lived more than 6 million years ago (MA). They were omnivorous, lived in jungles, measured 1.4 meters, were bipedal, and were descendants of the current chimpanzees, but with differences in the pelvis, humerus, and femur.
2. Ardipithecus ramidus:

INDUCTION / magnetic flux density: the number of lines of force crossing the unit area.

Paramagnetic material: when placed in a magnetic field and become magnets are oriented in the same direction as the field. Magnetic field to cease its magnetism disappears. (weakly attracted) Cr, Al ..

Diamagnetic material: when placed inside a magnetic field, are magnetized in the opposite direction to the field. These substances are called diamagnetic and their property is called diamagnetism. (weakly repelled) Na, Cu, N, H. .. .

Ferromagnetic materials: the electron spins tend to align because of the forces between them and form small regions called domains. By placing these substances under the action of a field, partially oriented domains and grow... Continue reading "Understanding Magnetic Materials: Flux, Saturation, and Permeability" »

Michelangelo's David is a monumental sculpture depicting the biblical King David. Rendered in a classical style, he is completely nude and portrayed as an athlete, carrying a sling in his left hand (resting on his shoulder) and a stone in his right. Facial features are clearly visible, along with curly hair, defined musculature, and a pronounced contrapposto.

Symbolic Analysis of David

Michelangelo depicted King David not merely as a young athlete, but as a man in the prime of his life. The artist chose as the subject of the work the moment prior to the confrontation between David and Goliath, unlike other representations where Goliath's defeated head often appears at his feet. Therefore, the figure displays a contained and expectant gaze, imbuing... Continue reading "Michelangelo's David: Form, Symbolism, and Florentine Identity" »

Aristotle's Cosmic Conception

Aristotle, in the fourth century BC, distinguished two regions of the universe:

The Terrestrial Region (Below)

• Earth occupies the center of the universe.
• All terrestrial bodies are formed by combining four elements: earth, water, air, and fire.
• Earth is the heaviest element and tends downwards, while fire tends upwards.

The Celestial Region (Above)

• It consists of transparent, concentric spheres surrounding the Earth.
• In each sphere, one of the heavenly bodies (Sun, Moon, Venus, etc.) is located.
• The outermost sphere contains the fixed stars.

Ptolemy's Geocentric System

Developed by Ptolemy (2nd Century AD), this system placed Earth at the center of the universe and described the movements of celestial bodies using Earth as... Continue reading "Evolution of Astronomical Models: From Ancient Cosmos to Newton" »

Early Greek Conceptions: The Ionian School

Some Greek thinkers made the first attempts to conceive the world as the result of natural processes, rather than an incomprehensible work of the gods. This was notably the case for the philosophers of the Ionian school, which flourished around the 6th century BC.

According to their views, the universe was initially in a state of primordial unity, where everything was mixed. From this unity, pairs of opposites arose, interacting with each other. These interactions led to the formation of heavenly bodies on one hand, and the Earth with its plants and animals on the other.

The Ionian philosophers conceived the Earth as a flat disk floating in the center of the celestial sphere.

The Spherical Earth: Pythagoras