phy

• Electromagnetic waves

  A) X-rays

  B) UV

  C) IR

  D) 400

  E) 700

  F) Microwave

  G) Long radio waves

  H) Radio waves

  
• Magnetic flux Φ (scalar) is the number of field lines enclosed by a loop

  Unit: Wb / T m²

  Φ=BA

  Magnetic flux density B (vector) is the magnetic flux per unit area in the cross section of the field (Φ/A) (ie the strength of the magnetic field)

  Unit: T / Wb m⁻²
• Brown wire: live

  Blue wire: neutral

  Green/yellow: earth

  
• Luminous flux Φ(lm): brightness of a source
• Illuminance E(lx/lm m⁻²): how much light is incident on a surface

  E=Φ/A

  however light is usually not a uniform field (cuz point source), thus inverse-square law is needed

  
• Lyman series(UV): nth excited state to 1st

  Balmer series(visible+UV): nth excited state to 2nd

  Paschen series(infrared): nth excited state to 3rd
• OTTV(overall thermal transfer value): the rate of heat gain per unit area through the building envelope, averaged over one year

  
• radioactive decay constant for a nuclide is defined as the probability per unit time that a given nucleus of that nuclide will decay by that mechanism