# Planck's constant has the dimension of:

38 views
in Physics
closed
Planck's constant has the dimension of:
1. Force
2. Energy
3. Linear momentum
4. Angular momentum

by (24.2k points)
selected

Correct Answer - Option 4 : Angular momentum

Concept:

• Planck's Constant (h): Light is said to be made up of small particles with zero rest mass known as photon. The energy of such photon is related with its frequency by Planck's constant.

E = h ν

E is energy, ν is the frequency of the photon.

• Dimensional Formula: It depicts the way to relate any unit to fundamental Units.
• If we have to find The dimensional formula of any quantity, At first, we find its units in terms of these fundamental units, and then replace units with these dimensions.
• Angular Momentum: The angular momentum of a body of mass m moving with speed v with radius of circular path r is

L = m v r

• The dimensional formula for angular momentum will be

(Dimension of mass)(Dimension of speed)(Dimension of radius) =  M L T -1 L = M L 2 T -1

Explanation:

Planck's constant can be given as

$h = \frac{E}{\nu}$

The Dimensional Formula of Energy is M L 2 T - 2

The dimension of Frequency is T - 1

The dimension of Planck's constant hence

$H = \frac{ML^2 T^{-2}}{T^{-1}}$

⇒ H = M L 2 T -1

This the dimension of angular momentum.

So, angular momentum is the correct option.

• Dimensional formula for Energy can be found using any expression for energy, for example, the expression for kinetic energy $K = \frac{1}{2} mv^{2}$
• Similarly, the dimensional formula of frequency can be obtained by relating it to the time period $f = \frac{1}{T}$
• Similarly, the dimensional formula for any units can be obtained.

 Fundamental Units Dimensions Mass M Length L Time T Temperature K Current A