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

CRT Screen Dimensions

The dimensions of the CRT screen are now standard in most instruments, measuring 10 cm in the horizontal axis (X) by 8 cm in the vertical (Y). On the screen, divisions of 1 cm square are recorded, either directly on the CRT or on a superimposed part featuring a grid of 80 cm square. This grid serves as the reference for the signal representation applied to the oscilloscope.

Appliance Description

The device consists of an evacuated glass tube containing:

• An electron beam dispenser at one end.
• A screen coated with phosphorescent material at the other end.
• Two pairs of parallel plates (one horizontal and one vertical).

Beam Deviation Formula

The beam deviation experienced is defined as:

y = (1/2) * (m/d) * (v0^2) * (E/V)

RMS Voltage

The Cartesian Scientific Method

The Scientific Method is a strict deductive method, particularly involving the idea of God as the creator and curator of the world and the immutability of certain innate ideas existing in the human mind, hitherto the prescient procedure of experience. It comes in addition to the cause and effect in physics, as it is a long series of deductive chains ordered by the prime causes. The concept of cause becomes substance next to the second key concept of Cartesianism, but that inference has limited contingents arrived at in moments and can no longer be deducted towards their cause; that is when experience intervenes to determine regarding its effects, which are those that are actually performed. Experience is valuable... Continue reading "Descartes' Scientific Method and Cartesian Physics" »

The Electron and Electric Current

The electron is the fundamental element of the electric current, as it has electric charge and can move from one atom to another.

Electrostatic Force (Coulomb's Law)

The force of attraction or repulsion between two charged bodies is directly proportional to the product of their charges and inversely proportional to the square of the distance that separates them.

A coulomb is the charge that a body possesses when, facing another body of the same charge at 1 meter distance in a vacuum, it repels with a force of $9.10^9$ N.

Electric Circuit Components

An electric circuit consists of a set of interconnected elements, so as to permit the permanent circulation of electric power.

• Generator: Is the device responsible for

Calculating Laser Beam Size

It is simple to calculate the size of a laser beam. For example, if the divergence is 2 mils, after the beam has traveled 10 meters, its radius is 20 mm and its diameter is 40 mm.

Laser Coherence and Wave Properties

Electromagnetic radiation is an oscillatory phenomenon. The electric and magnetic fields oscillate in a sine wave over time. However, these oscillations do not remain constant for long and are not always the same at all points in the space occupied by the light. The degree of relationship between these oscillations at different times and in different positions defines the coherence of radiation.

The coherence of the radiation determines the visibility of interference phenomena (the constructive superposition... Continue reading "Laser Beam Properties, Coherence, and Efficiency" »

Amplification of Light in Lasers

All lasers contain a substance that can increase the intensity of light passing through it.

The Active Medium

This substance is called the active medium and may be a solid, liquid, or gas. The mechanism by which the active medium increases the intensity will be explained later. For the moment, assume that light amplification is possible.

For example, in a YAG laser (Nd:YAG), the active medium is a Yttrium Aluminum Garnet (YAG) bar containing neodymium ions.

Understanding Gain

The factor by which the light intensity increases in the active medium is known as gain.

The gain is not constant for a particular type of medium; it depends on:

• The wavelength of light.
• The length of the active medium.
• The extent to which the active

Fundamental Astronomical Concepts

Planetary Models

• Geocentric System: A global model that claims Earth is the center of the universe, around which the sun and other planets revolve.
• Heliocentric System: A planetary model that assumes the sun is the center of our system, around which other planets, including Earth, revolve.

Astrophysics and Cosmology

• Astrophysics: The branch of astronomy that studies the structure, composition, and evolution of stars.
• Cosmology: The branch of astronomy that studies the structure, origin, and evolution of the universe.

Space and Time

• Light-Year: The distance light travels in one year in a vacuum at a velocity of 300,000 km/s, approximately 9.5 trillion km.
• Big Bang Theory: A model that explains the formation of the universe

Uniform Circular Motion

There are many everyday movements that are familiar and not rectilinear. We focus here on circular motion.

Arc and Angle

In circular motion, a mobile object covers an arc of the trajectory while simultaneously traveling through an angle. The radian is the value of the central angle that subtends an arc whose length is equal to the radius.

Angular Velocity

This is the relationship between the angle turned and the time spent; this magnitude is similar to the speed of rectilinear movement.

Angular Acceleration

This is the relationship between the variation of angular velocity and the time spent to effect it.

Normal or Centripetal Acceleration

This vector may be constant in magnitude but not in direction. It is perpendicular to the... Continue reading "Principles of Uniform Circular Motion and Dynamics" »

Abbe Operation

Abbe Operation is based on the determination of the critical angle. The technique is to calibrate the device, usually with distilled water at 20ºC, by matching the shade formed by the prism surface illuminated by a brand (not recorded) in the center of the telescope. Perform the same operation with the test sample to make the correct reading of the refractive index in the eyepiece of the telescope. Since the refractive index varies with temperature, it is important to perform the measurement with the apparatus thermostatted at 20°C or at least know the temperature at which to make the determination.

Understanding Light Polarization

• Natural Light: It is a vibration in all directions perpendicular to the beam.
• Polarized Light: It

Gravitational Acceleration and Field Strength

The strength of the gravitational field depends on the amount of mass $M$ causing the field. Let us define a characteristic of the field that depends only on the mass $M$ and the distance $r$ to the point we consider.

Defining Gravitational Field Strength ($g$)

The gravitational field strength, $g$, at a point in space is the force that would act on a unit mass located at that point. Its unit is Newtons per kilogram ($N/kg$). This term is often used interchangeably with gravitational field intensity.

Calculating the Gravitational Field

To determine the gravitational field created by a point mass $M$, we place a test mass $m$ at a point $P$ in space at a distance $r$ from mass $M$. We calculate the force... Continue reading "Fundamentals of Gravitational Force and Field Calculation" »

Energy: Ability to Do Work

Energy: the ability to do work. Energy is a physical quantity that measures the capacity of a system to produce change or perform work.

Energy in Other Sciences

In other sciences, energy is a scalar quantity that is assigned to the state of a physical system. It is used to describe and compare states across different fields and contexts.

Importance of Energy: Life and Health

Importance of energy: life and health depend on energy. Energy helps us and enables work; it is vital for many essential processes and is fundamental to the operation of systems — without energy, many functions would not exist.

Examples of Energy

• Kinetic energy: quantified according to the motion of matter.
• Chemical energy: associated with chemical