Candela was chosen so that the new definition would precisely match the old definition. Although the candela is now defined in terms of the second (an SI base unit) and the watt (a derived SI unit), the candela remains a base unit of the SI system, by definition. If a source emits a known luminous intensity "I" (in candelas) in a well-defined cone, the total luminous flux "Φ" in lumens is given by where "A" is the "radiation angle" of the lamp—the full vertex angle of the emission cone. For example, a lamp that emits 590 cd with a radiation angle
Does exactly what it says on the tin Does exactly what it says on the tin "It does exactly what it says on the tin" was originally an advertising slogan in the United Kingdom, which then became a common idiomatic phrase. It colloquially means that the name of something is an accurate description of its qualities. It is akin to the previously existing phrases "by name and by nature" and "it lives up to its name". It originated in a series of television advertisements by the woodstain and wood-dye manufacturer Ronseal, initiated in 1994 and still being broadcast . The slogan was created by Liz Whiston and Dave