Iam confused on how this table works

A150 w lamp emits light of wavelength 590 nm uniformly in all directions. what is the photon flux (photons per unit area per unit time) on a small screen at a distance 2.3 m from the lamp? assume the photons are uniformly distributed over the surface of a sphere of radius 2.3 m.

If steel is more dense that lake water, why can a boat float

Positrons are spontaneously emitted from the nuclei of