7.(3 pts) Fill n the table for the following three electron transitions: Electro

Question

7.(3 pts) Fill n the table for the following three electron transitions: Electron ransition Indicate with an "X Shortest Wavelength Longest Wavelength Are Photons: Visible (vis) Ultraviolet (UV) or Infrared (IR) n2 to n-1 n=3 to n-2 n=4 to n=3 8. ( 1 pt) A student performs this experiment and obtains a value of, 1 .97 x 10-18 J, for, RE· Calculate the student's % error. 9. (1 pt) Consider the whole electromagnetic spectrum, why do we use sunscreen to protect ourselves from the UV rays of the sun or a "lead coat" to protect ourselves from x-rays? 10. (1 pt) Why do we NOT need to protect ourselves when standing in front of a conventional oven that emits infra-red electromagnetic waves? 11. (2 pts) Draw an energy diagram with up and down arrows showing ALL the possible excitation and relaxation transitions for a photon with three possible energy levels. hv photon emission hv photon absorption EXCITATION RELAXATION

Explanation / Answer

Q7

Apply Rydberg Formula

E = R*(1/nf^2 – 1/ni ^2)

R = -2.178*10^-18 J

Nf = final stage/level

Ni = initial stage/level

E = Energy per unit (i.e. J/photon)

a)

nf = 1, ni = 2

E = (-2.178*10^-18)*(1/1^2 – 1/2 ^2)

E = 1.633*10^-18

For the wavelength:

WL = h c / E

h = Planck Constant = 6.626*10^-34 J s

c = speed of particle (i.e. light) = 3*10^8 m/s

E = energy per particle J/photon

WL = wavelength in meters

WL = (6.626*10^-34)(3*10^8)/(1.633*10^-18)

WL = 1.2172*10^-7 m

to nanometers:

WL = (1.2172*10^-7)(10^9) = 121.72

b)

nf = 2, ni = 3

E = (-2.178*10^-18)*(1/2^2 – 1/3^2)

E = 3.025*10^-19

For the wavelength:

WL = h c / E

h = Planck Constant = 6.626*10^-34 J s

c = speed of particle (i.e. light) = 3*10^8 m/s

E = energy per particle J/photon

WL = wavelength in meters

WL = (6.626*10^-34)(3*10^8)/(3.025*10^-19)

WL = 6.5712*10^-7 m

to nanometers:

WL = (6.5712*10^-7)(10^9) = 657.12 nm

c)

nf = 3, ni = 4

E = (-2.178*10^-18)*(1/3^2 – 1/4^2)

E = 1.0587*10^-19

For the wavelength:

WL = h c / E

h = Planck Constant = 6.626*10^-34 J s

c = speed of particle (i.e. light) = 3*10^8 m/s

E = energy per particle J/photon

WL = wavelength in meters

WL = (6.626*10^-34)(3*10^8)/(1.0587*10^-19)

WL = 1.877*10^-6 m

to nanometers:

WL = ( 1.877*10^-6)(10^9) = 1877 nm

clearly,

longest wavleength = 4 to 3; shortest wavelength is 2 to 1

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