Revolutions per minute velocity. The corresponding basic SI derived unit is s or Hz. When measuring angular speed, the unit radians per second is used. Formally, hertz (Hz) and radian per second (rad/s) are two different names for the same SI unit, s. However, they are used for two different but proportional ISQ quantities: frequency and angular frequency (angular speed, magnitude of angular velocity). The conversion between a frequency (measured in hertz) and an angular velocity (measured in radians per second) are: Thus a disc rotating at 60 rpm is said to be rotating at either 2 rad/s or 1 Hz, where the
Einstein (unit) as, "The photon flux was 1500 μmol m s". This unit was named after physicist Albert Einstein. Einstein (unit) The einstein is a unit defined as one mole () of photons. As such, photosynthetically active radiation (PAR) was formerly often reported in microeinsteins per second per square meter (μE m s). This usage is also not part of the International System of Units and when used this way it is redundant with the mole. Since the unit does not have a standard definition and is not part of the SI system, it is usually better to avoid its use. The