The eyes of certain reptiles pass a single visual signal to…

The eyes of certain reptiles pass a single visual signal to the brain when the visual receptors are struck by photons of a wavelength of 705 nm. 1) What’s the energy of a single photon? 2) If a total energy of 1.15×10–14 J is required to trip the signal, what is the minimum number of photons that must strike the receptor? Mark your answer next to words “Final answer is”. You must follow significant figure rules.   You must show your work here to receive any credit (you may receive 0 points for only showing your final answer).

An unknown element has two naturally occurring isotopes with…

An unknown element has two naturally occurring isotopes with masses 18.00 amu (A) and 21.00 amu (B) and has an atomic mass of 19.90 amu.  What’s the natural abundance of isotope A (%)?  Mark your answer next to words “Final answer is”. You must follow significant figure rules.   You must show your work here to receive any credit (you may receive 0 points for only showing your final answer).