1Which of these has the same dimensions as power of a lens?
Power of a lens and wave number both have the dimensions [L⁻¹].
OpticsClass 12, Ray Optics and Optical Instruments
Dimensional formula of Power of a lens
[L-1]
One over the focal length in metres. It is a different quantity from mechanical power.
How to get the dimensional formula of power of a lens
- Start from the definition: power of a lens = 1 / focal length.
- focal length = length, so focal length is [L] = [L].
- Put in the dimension of each part: 1 / [L].
- Add the powers of each base quantity: [L-1].
Quantities with the dimensions [L⁻¹]
Equal dimensions do not make them the same quantity. Compare power of a lens with the others in the full grid.
Three questions on power of a lens
2What is the SI unit of power of a lens?
The SI unit of power of a lens is the dioptre (D).
3Which one has different dimensions from the others?
Fringe width is [L]. The other three are all [L⁻¹].
Power of a lens: quick answers
What is the dimensional formula of power of a lens?
The dimensional formula of power of a lens is [L⁻¹]. It comes from power of a lens = 1 / focal length.
What is the SI unit of power of a lens?
The SI unit of power of a lens is the dioptre (D).
Which quantities have the same dimensions as power of a lens?
Power of a lens shares [L⁻¹] with wave number, Rydberg constant. Equal dimensions do not make them the same quantity.