Day 3 Pre-Reading

Energy

The capacity to do work.

Power

The rate at which energy is flowing.

What does 1 W equal?

1 J/s

What does 1 Hp equal?

740 W

Internal Energy

How fast the atoms and molecules in the object are moving.

Temperature

A measure of the internal energy of an object.

Unit conversion from Celsius to Kelvin

K = C + 273.15

Photons

Small discrete packages of energy.

Wavelength

Characteristic size.

Visible

Seen with the human eye.

Infrared

Beyond the red end of the visible spectrum.

Ultraviolet

Wavelength is beyond the violet end of the visible spectrum.

Blackbody

Idealized physical body that absorbs all incident electromagnetic radiation.

Wien’s Displacement Law

Relationship between an object’s temperature and the peak of its emission spectrum.

Wien’s Displacement Law Formula

λ_max = 2897/T

T = Temperature (K)

λ_max = Wavelength of the peak of the emission spectrum (µ)

Stefan-Boltzmann Equation

Relationship between the total power radiated by a blackbody and temperature.

Stefan-Boltzmann Equation Formula

P/a = σT⁴

P/a = Power emitted by a blackbody unit of surface area (W/m²)

σ is the Stefan–Boltzmann constant, σ = 5.67 x 10 -⁸ W/m²/K⁴

T = Temperature (K)

What happens to internal energy and temperature when E_in > E_out?

Increases

What happens to internal energy and temperature when E_out > E_in?

Decreases

What happens to internal energy and temperature when E_out = E_in?

Not changing

Where in the EM spectrum is the visible range?

C

Grey Body

A real-world object that, like a blackbody, has a spectral distribution of radiation that is a constant fraction of a blackbody's radiation at the same temperature, but that fraction is always less than one, making it an imperfect emitter.