Einstein is most famous for his Theory of Special Relativity andthe resulting eq

Question

Einstein is most famous for his Theory of Special Relativity andthe resulting equation E=mc2. However, he wasawarded the Nobel Prize for his explanation of the photoelectriceffect, which relied on the particle nature of light. Byexperiment it has been found that it takes light with a minimumenergy of 3.7 x 10-19 J to eject electrons fromsodium metal and light with a minimum energy of 7.5 x10-19 J to eject electrons from copper.
a) If violet light with a just visible short wavelength of 400nm falls on each metal, what would be the energy of the ejectedelectrons? b) What would be the energy of the ejected electrons if redlight with a long wavelength of 750 nm falls on the metals?
a) If violet light with a just visible short wavelength of 400nm falls on each metal, what would be the energy of the ejectedelectrons? b) What would be the energy of the ejected electrons if redlight with a long wavelength of 750 nm falls on the metals?

Explanation / Answer

Minimum energy to eject electrons from sodium metal W=3.7*10 ^ -19 J wavelength = 400 * 10 ^ -9 m energy of th ephoton E = hc / where h = planck's constant = 6.625 * 10 ^ -34 Js          c = speed oflight = 3* 10 ^ 8 m / s plug the values we get E = 4.968*10^-19 J energy of the ejected eletron K = E - W = 1.268*10^-19 J Minimum energy to eject electrons from coppermetal W= 7.5*10 ^ -19 J wavelength = 400 * 10 ^ -9 m energy of th ephoton E = hc / where h = planck's constant = 6.625 * 10 ^ -34 Js          c = speed oflight = 3* 10 ^ 8 m / s plug the values we get E = 4.968*10^-19 J Since E < W i.e., the electron not ejected fromthe copper surface similarly you do for red light wavelength = 400 * 10 ^ -9 m energy of th ephoton E = hc / where h = planck's constant = 6.625 * 10 ^ -34 Js          c = speed oflight = 3* 10 ^ 8 m / s plug the values we get E = 4.968*10^-19 J energy of the ejected eletron K = E - W = 1.268*10^-19 J Minimum energy to eject electrons from coppermetal W= 7.5*10 ^ -19 J wavelength = 400 * 10 ^ -9 m energy of th ephoton E = hc / where h = planck's constant = 6.625 * 10 ^ -34 Js          c = speed oflight = 3* 10 ^ 8 m / s plug the values we get E = 4.968*10^-19 J Since E < W i.e., the electron not ejected fromthe copper surface similarly you do for red light Minimum energy to eject electrons from coppermetal W= 7.5*10 ^ -19 J wavelength = 400 * 10 ^ -9 m energy of th ephoton E = hc / where h = planck's constant = 6.625 * 10 ^ -34 Js          c = speed oflight = 3* 10 ^ 8 m / s plug the values we get E = 4.968*10^-19 J Since E < W i.e., the electron not ejected fromthe copper surface similarly you do for red light wavelength = 400 * 10 ^ -9 m energy of th ephoton E = hc / where h = planck's constant = 6.625 * 10 ^ -34 Js          c = speed oflight = 3* 10 ^ 8 m / s plug the values we get E = 4.968*10^-19 J Since E < W i.e., the electron not ejected fromthe copper surface similarly you do for red light

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