Key Concepts in Modern Physics: A Concise Review
Key Concepts in Modern Physics
This document outlines fundamental concepts in modern physics.
1. Black Body Radiation
A black body is an ideal object that absorbs all electromagnetic radiation that reaches it. T is the body’s temperature, and k is the electromagnetic energy emitted due to that temperature. The wavelength of black body radiation follows two laws:
- Wien’s Law: Intensity decreases with increasing temperature.
- Stefan-Boltzmann Law: The intensity of radiation emitted by a black body is proportional
Quantum Physics: Key Concepts and Phenomena
Quantum Physics
1. Thermal Radiation and Black-body Radiation
The electromagnetic energy emitted by a body due to its temperature is called thermal radiation. Thermal radiation varies with temperature and the composition of the body. Bodies whose thermal radiation depends *only* on temperature are said to exhibit black-body radiation and have the following characteristics:
- The total power (P) emitted by a surface at temperature (T) satisfies the Stefan-Boltzmann Law: (where σ = 5.67 x 10-8 W/m2K4)
Friction, Photosynthesis, Matter, and Scientist
Friction
Newton’s Laws:
- 1st: An object remains at rest, or in motion at a constant speed in a straight line, unless acted upon by an external force.
- 2nd: Force = Mass * Acceleration
- 3rd: For every action, there is an equal and opposite reaction.
Velocity: Velocity is the speed in combination with the direction of motion of an object.
Positive Acceleration: Positive acceleration occurs when an object is speeding up in the positive direction. For example, if a car is moving forward and its velocity is increasing,
Read MoreUnderstanding Wave Motion: Types, Properties, and Phenomena
Wave Motion
Wave motion is the propagation of a disturbance of some physical magnitude through space. In wave motion, there is transportation of energy and momentum, and the particles successively reached by the wave vary their state.
Wave Types
Waves are classified by:
Nature
- Mechanical: These waves need a material medium for the disturbance to propagate (e.g., sound waves, water waves).
- Electromagnetic: These waves do not need a material medium and can propagate in a vacuum (e.g., light rays, X-rays)
Understanding Speed, Velocity, and Acceleration
Speed is simply how fast you are going, with no regard to direction. Velocity, however, must also have the direction specified. Both are measured in m/s, km/h, or mph.
- Average speed = Distance moved ÷ Time taken (s = v × t)
- Acceleration = Change in velocity ÷ Time taken ((v-u) = a × t, v² = u² + 2as)
Distance-Time Graphs
- Flat sections indicate the object is stopped.
- A steeper graph means the object is moving faster.
- Curves represent acceleration.
- A curve getting steeper means speeding up.
- A leveling-
Gravitational, Electric, and Magnetic Fields
Here’s a comparison of gravitational, electric, and magnetic fields:
Field Characteristics
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Gravitational Field:
- A field of forces acting on bodies with mass.
- The force exerted is proportional to the mass acted upon.
- The gravitational force is always attractive.
- The field is defined at each point by the vector field g = F / m.
- The gravitational field strength due to a point mass is inversely proportional to the square of the distance: g = G · m/r2.
- The universal gravitational constant (G) is the same in