Question

For the period 1960-1983, the metre was defined to be 1,650, 763 73 wavelengths of a certain orange red light emitted by atoms. Compute the distance of the wavelength in nanometres to the correct number of significant figures.​

Answer 1

Answer:

The energy of a photon is given by E=hf, where h is the Planck constant and f is the frequency. The wavelength λ is related to the frequency by λf=c, so E=hc/λ.

Since,

h=6.626×10

−34

J⋅s and c=2.998×10

8

m/s

hc=

(1.602×10

−19

J/eV)(10

−9

m/nm)

(6.626×10

−34

J⋅s)(2.998×10

8

m/s)

=1240eV⋅nm

Thus,

E=

λ

1240eV⋅nm

With

λ=(1,650,763.73)

−1

m=6.0578021×10

−7

m=605.78021nm

we find the energy to be

E=

λ

hc

=

605.78021nm

1240eV⋅nm

=2.047eV