Converting Armstrongs to Joules

Converting Armstrongs to Joules

  • To convert Armstrongs to Joules, you need to use the constant 6.625×10−346.625 \times 10^{-34} (presumably Planck's constant, hh) and the speed of light, cc, which is 3×1083 \times 10^8 meters per second in MKS units.

  • The formula to convert from wavelength (λ\lambda) to energy (in Joules) is E=hcλE = \frac{hc}{\lambda}.

Converting Angstroms to Meters

  • If the wavelength (λ\lambda) is given in Angstroms ("), you need to convert it to meters first.

  • 1 Angstrom (") is equal to 10−1010^{-10} meters. Therefore, to convert xx Angstroms to meters, you multiply xx by 10−1010^{-10}. That is: x A˚=x×10−10 metersx \text{ Å} = x \times 10^{-10} \text{ meters}.

Units and Calculation

  • Correct Units: Make sure to use consistent units (MKS - meters, kilograms, seconds) to obtain the energy in Joules.

  • hh has units of Joule-seconds (J\cdot s).

  • cc has units of meters per second (m/s).

  • λ\lambda has units of meters (m).

  • Dimensional Analysis:

    • E=hcλ=(J⋅s)×(m/s)m=JE = \frac{hc}{\lambda} = \frac{(\text{J} \cdot \text{s}) \times (\text{m/s})}{\text{m}} = \text{J}
    • The units of seconds and meters cancel out appropriately, leaving Joules as the unit for energy.