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
Optical Amplifiers: EDFA, Raman, and SOA
EDFAs use a pump laser (980 nm or 1480 nm) to bring electrons up to a higher energy level. Signal amplification is achieved by emitted photons of the same signal wavelength with the help of stimulated emission.
EDFA Parameters
- Gain: Ratio of the input power to the output power (in dB)
- Bandwidth: Range of wavelengths in which amplification is obtained
- Gain Saturation: Point at which the output power ceases to grow with respect to the increase in input power
- Noise Figure: Ratio of the SNR at the input