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

Photons and Electrons in the Double Slit Experiment

Evidence for Wave-Particle Duality

• A single electron or photon leaves the source with particle-like discreteness and creates a single discrete spot on the screen.
• The interference pattern, which occurs over time, is a wave property.

Diffraction Pattern and Heisenberg’s Uncertainty Principle

• We cannot measure the exact position of each electron or its exact momentum as it approaches the slit; there is uncertainty in both position and momentum.
• The uncertainty in each electron’s y-position is reduced to the width of the slit (since we are certain it passes through the slit). This increases its uncertainty in the momentum of the y-direction.
• The uncertainty in the momentum in the y-direction means

Understanding Physical Forces

A force is the interaction of a body with something external to it and is capable of:

• Modifying its state of motion or rest (we will focus on it).
• Causing deformation.

The Normal Force

The normal force (N) is a reaction force; it is a force resulting from the application of Newton’s third law, which must have exactly the value required for the net force along its axis to be null.

Newton’s Laws of Motion

Newton’s First Law

Newton’s first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This tendency to resist changes in a state of motion is inertia.

Newton’s Second Law

Newton's second law of motion can... Continue reading "Fundamental Principles of Forces and Motion" »

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Anatomy of the Eye

The retina of the eye, lining the posterior two-thirds of the eyeball, is located within the inner tunic.

The jelly-like substance located between the lens and retina is the vitreous body.

True or false: Accommodation refers to the change in lens thickness in order to provide fine focus of an image. The answer is true.

Functions of the Vitreous Body:

• Maintains shape of eyeball
• Refracts rays of light
• Keeps retina smoothly pressed against inner surface of eye chamber

Hemidecussation occurs within the visual projection pathway at the optic chiasm.

The position time and velocity-time graphs represent the position occupied by a mobile object with respect to a reference system. Are also used to represent it's velocity over time. If we imagine that the mobile objects moves in a straight line, 2 types, of graph can be used:The distance (s) of the mobile object from the origin is always the same over time (t), which means the mobile object is at rest  The distance (s) increases uniformly over time (0). On the green line, the mobile object leaves the origin (0), but on the red line begins to move at a distance (s) from the origin  The distance to the ongin (0) is reduced over time (1) Therefore, the mobile object is moving towards the reference point..Velocity time graph ..It indicates the... Continue reading "Understanding Motion Graphs: Position, Velocity, and Time" »

PET Scan Principles

• 31. The detector array of a PET detects: a. Two gamma rays on opposite sides.
• 32. Which is NOT a common chemical element or molecule used as a radioisotope in PET? d. Hydrogen.
• 33. Which is NOT an indication for a PET scan? d. Gastrointestinal transit.
• 34. Why is it important to be punctual for a PET test? b. Due to the radioactive decay of the radioisotopes.

Radiotherapy and LINAC Systems

• 35. In which type of teletherapy is there no exit dose? a. Proton.
• 36. Which is NOT a part of a LINAC? c. Detector array.
• 37. Which equipment is used in proton beam radiotherapy? d. Cyclotron.
• 38. Which type of teletherapy is used prior to surgery? d. Neo-adjuvant.
• 39. Which is a common short-term side effect of neck cancer treatment? b. Mucositis.

Fundamental Forces in Physics

Weight (W)

• Weight is the gravitational force that exists between masses. Specifically, it is the force exerted on an object by a planet's gravity when the object is at the planet's surface.
• It can be calculated using the formula: W = mg
  • Where: m is the mass of the object under study, measured in kilograms (kg) in the SI unit system.
  • g is the acceleration due to gravity at the planet's surface. On Earth, g ≈ 9.81 m/s².
• Weight is directed along the line connecting the object under study with the planet's center, oriented towards the planet's center.

Normal Force (N)

• The Normal Force is a contact force that acts between two surfaces that are touching each other.
• It is often calculated indirectly, as it balances other forces

Review

1 Balancing Moments

• seesaw: sube y baja 4
• Perpendicular: At a 90 degree angle to something
• Newton: The unit of measurement of force
• Clockwise: In the same direction as the movement of the hands on a clock
• Counterclockwise: In the opposite direction to the movement of the hands on a clock

Diagram

• a-You have to calculate the moment
• b-The wheel turns more easily when you spin it from near the rim. The distance

M=fd
F=30N
M=fd

Left is 2FI, same result
d=15cm
M=(30) (0.15)=4.5

Right is 2dF, same result
0.15m
M=4.5Nm

2 Making a Scale

• Spring constant: A measure of how stiff or strong a spring is
• Extension: The increase in the length of something
• Elastic: A material able to resume its original shape after being stretched or compressed
• Elastic Limit: The extent to

What is Force?

Force is a push or pull that can deform an object or change its state of rest or motion.

Types of Forces

• Contact
• Non-contact
• Instantaneous
• Constant

Formula of Force

F = m • a

Difference Between Force and Weight

Weight is a force. Everything on Earth is pulled down towards the ground by gravity. The weight of an object is how hard gravity pulls down on it.

Larger objects get pulled more strongly, so they weigh more than smaller objects. When scientists want to talk about how much stuff is inside something, they talk about mass.

Causes of Force

Forces arise when two or more bodies come into contact. For example, when there is a crash or when you push a door.

Bodies, even if they are not in contact, exert a force on others. For example, the... Continue reading "Understanding Force, Motion, and Newton's Laws" »