Question

The value of Planck's constant is

• A. $6.63 \times 10^{-34} J/sec. $
• B. $6.63 \times 10^{-34} kg-m^2/sec $
• C. $6.63 \times 10^{-34} kg-m^2 $
• D. $6.63 \times 10^{-34} J-sec .$

Answer 1

The Correct Option is B

The question asks for the correct value of Planck's constant. Planck's constant is a fundamental constant in quantum mechanics, which relates the energy of a photon to its frequency. The standard and widely accepted value of Planck's constant is:

• $h = 6.63 \times 10^{-34} J \cdot s$

This means that the correct value in terms of units as joules times seconds (J \cdot s) is given in the options. Let's analyze the given options to find the correct one:

1. $6.63 \times 10^{-34} J/sec.$ - This option involves incorrect units. The units should be joules times seconds, not joules per second.
2. $6.63 \times 10^{-34} kg-m^2/sec $ - This option is incorrect. Planck's constant is not expressed in kilogram meter squared per second.
3. $6.63 \times 10^{-34} kg-m^2 $ - This option is incorrect as well. Planck's constant should not have the unit kilogram meter squared.
4. $6.63 \times 10^{-34} J-sec. $ - This is the correct representation of Planck's constant.

Therefore, the correct answer is $6.63 \times 10^{-34} J-sec.$. Planck's constant has dimensions of energy (joule) multiplied by time (second), making the correct dimensional representation as joule-seconds.