need help on 3 h.w problems?

Question

1. Cobalt-60 is radioactive isotope use to treat cancers of the brain and other tissues. A gamma ray emitted by an atom of this isotope has an energy of 1.33 MeV ( million-electron volts 1eV= 1.602 X 10^-19. What is the frequency in (Hz) and wavelength in (m) of this gamma ray?

2.A microwave emits photons with a wavelenght of 1.55 X 10^-2m. What is the energy of each photon in J?

3.What is the energy of a photon of blue light of wavelength 475nm in J?

Answer 1

1) E= hf so f=E/h the problem is to,use correct units
1 eV = 1.6*10^-19J and
1.33 MeV= 1.33*1.610^6*10^-19=2.128*10^-13 J
f =2.128*10^-13/6.62 *10^-34=3.215*10^20Hz
and wavelength = c/f = 310^8/3.215*10^20=9.33*10^-13m

2) E=hc/wavalength = 6.62*10^-34*310^8/1.55*10^-2=1.281*10^-23J

3)same formula than 2
E= 6.62*10^-34*310^8/475*10^-9 =4.181*10^-19J

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