Number of zeroes in the number 3.146 × 1020 are______
18
20
15
17
A 100 Watt bulb emits monochromatic light of wavelength 400 nm. Calculate the number of photons emitted per second by the bulb.
How much time in hours it would take to distribute one Avogadro number of wheat grains if 1020 grains are distributed each second?