F=Gm1m2/D*2
or,2.0×10^-7 = (6.67×10^-11 ×75×90)/D^2
or,2.0×10^-7 = (45022.5×10^-11)/D^2
or,D^2=22511.25×10^-4
D=1.5003m
Answer:
an oxygen atom with 8 electrons, 8 protons and 9 neutrons
As frequency is inversely proportional to wavelength so first 2 options are wrong, shorter wavelength means higher energy so option d is correct
Well, that's really your place to figure out:)
