Planck's constant has the value 6.626 x 10^-34. Which unit combination correctly accompanies this value?

Planck's constant has the value 6.626 x 10^-34. Which unit combination correctly accompanies this value?

• A. 6.626 x 10^-34 J s
• B. 6.626 x 10^-24 J s
• C. 6.626 x 10^-34 J
• D. 6.626 x 10^-44 J s

Answer: (A)

Planck's constant is a quantum of action that links energy to frequency via E = hν. Since frequency has units of 1/s, h must carry energy times time units, i.e., joule-seconds (J·s). With the given value, h = 6.626 × 10^-34 J·s, multiplying by ν (in s^-1) gives E in joules: (J·s)(s^-1) = J. The other options fail because they either have the wrong exponent or lack the time unit, so they wouldn’t produce energy when combined with frequency.

Planck's constant is a quantum of action that links energy to frequency via E = hν. Since frequency has units of 1/s, h must carry energy times time units, i.e., joule-seconds (J·s). With the given value, h = 6.626 × 10^-34 J·s, multiplying by ν (in s^-1) gives E in joules: (J·s)(s^-1) = J. The other options fail because they either have the wrong exponent or lack the time unit, so they wouldn’t produce energy when combined with frequency.