5. What is the longest wavelength of a photon that can be emitted from a hydroge
ID: 1398150 • Letter: 5
Question
5.
What is the longest wavelength of a photon that can be emitted from a hydrogen atom in which the final state is n = 9? Let the Rydberg constant R = 1.097 × 107m-1.
22,000 nm
28,000 nm
7400 nm
39,000 nm
16,000 nm
6.
Photoelectrons are emitted from a metal surface when it is illuminated by light of wavelength less than 520 nm. Photoelectrons are not emitted when the wavelength is increased to a greater value than 520 nm. What is the metal's work function? Let 1 eV = 1.60 × 10-19 .J, the mass of an electron m = 9.11 × 1031 kg, the speed of light c = 3.00 × 108 m/s, and Planck’s constant h = 4.136 × 1015 eV s.
2.4 eV
3.0 eV
2.8 eV
2.6 eV
7.
Monochromatic light is incident on a metal surface and electrons are ejected. Then the intensity of the light is increased while the frequency is kept constant. What changes, if any, will occur to the ejection rate and maximum energy of the electrons?
greater rate; same maximum energy
greater rate; greater maximum energy
same rate; greater maximum energy
same rate; same maximum energy
5.
What is the longest wavelength of a photon that can be emitted from a hydrogen atom in which the final state is n = 9? Let the Rydberg constant R = 1.097 × 107m-1.
22,000 nm
28,000 nm
7400 nm
39,000 nm
16,000 nm
6.
Photoelectrons are emitted from a metal surface when it is illuminated by light of wavelength less than 520 nm. Photoelectrons are not emitted when the wavelength is increased to a greater value than 520 nm. What is the metal's work function? Let 1 eV = 1.60 × 10-19 .J, the mass of an electron m = 9.11 × 1031 kg, the speed of light c = 3.00 × 108 m/s, and Planck’s constant h = 4.136 × 1015 eV s.
2.4 eV
3.0 eV
2.8 eV
2.6 eV
Explanation / Answer
5)
for longest wavelength, n1 should be equal to 10.
1/lamda = R*(1/n2^2 - 1/n1^2)
1/lamda = R*(1/9^2 - 1/10^2)
1/lamda = R*0.002345
lamda = 1/(R*0.002345)
= 1/(1.097*10^7*0.002345)
= 390*10^-7 m
= 39000 nm
6) Work function, Wo = h*c/lamda
= 6.625*10^-34*3*10^8/(520*10^-9)
= 3.822*10^-19 J
= 3.822*10^-19/(1.6*10^-19) eV
= 2.4 eV
7) greater rate; same maximum energy
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