1Which of these has the same dimensions as luminous flux?
Luminous flux and luminous intensity both have the dimensions [cd].
OpticsClass 12, Ray Optics and Optical Instruments
Dimensional formula of Luminous flux
[cd]
Luminous intensity times solid angle. The steradian is dimensionless, so a lumen has the dimension of the candela.
How to get the dimensional formula of luminous flux
- Start from the definition: luminous flux = luminous intensity × solid angle.
- area = length × length, so area is [L] × [L] = [L2].
- solid angle = area / area, so solid angle is [L2] / [L2] = [M0 L0 T0].
- Put in the dimension of each part: [cd] × [M0 L0 T0].
- Add the powers of each base quantity: [cd].
Quantities with the dimensions [cd]
Equal dimensions do not make them the same quantity. Compare luminous flux with the others in the full grid.
Three questions on luminous flux
2What is the SI unit of luminous flux?
The SI unit of luminous flux is the lumen (lm).
3Do luminous flux and fringe width have the same dimensions?
Luminous flux is [cd] but fringe width is [L].
Luminous flux: quick answers
What is the dimensional formula of luminous flux?
The dimensional formula of luminous flux is [cd]. It comes from luminous flux = luminous intensity × solid angle.
What is the SI unit of luminous flux?
The SI unit of luminous flux is the lumen (lm).
Which quantities have the same dimensions as luminous flux?
Luminous flux shares [cd] with luminous intensity. Equal dimensions do not make them the same quantity.