Final answer:
The wavelength of red light is 7×10^-7 m. To express this in nanometers, multiply by 10^9 (the conversion factor from meters to nanometers). The answer is 700 nm.
Step-by-step explanation:
The wavelength of red light is given as 7×10-7 meters. To express this value in nanometers (nm), we use the fact that 1 nm equals 10-9 meters. Therefore, the conversion is done by multiplying the given wavelength by 109 (to convert meters to nanometers).
7×10-7 m × 109 nm/m = 700 nm
So, the wavelength of red light when expressed in nanometers is 700 nm, which corresponds to answer choice A. 700 nm.