Erythemal ultraviolet dose is reached by the exposure to the LE-30 lamp during 4 minutes at a distance of 1 m from the source. Calculate the exposure time required to receive the preventive dose at a distance of 5 meters from the source?

Suppose that a comet that was seen in 563 a.d. by chinese astronomers was spotted again in year 1951. assume the time between observations is the period of the comet and take its eccentricity as 0.986. what are (a) the semimajor axis of the comet's orbit and (b) its greatest distance from the sun?

Which is not true about oxygen-17 and oxygen-18?

If y gets smaller as x gets bigger and y have an relationship?