28) (a) h = 6.63 x 10-34 J•s c = 3.00 x 108 m/s
ni = 5 nf = 1
E = -2.18 x 10-18 J * (1/nf2 - 1/ni2)
E = -2.18 x 10-18 J * (1/12 - 1/52)
E = -2.09 x 10-18 J and because E is negative, energy is emitted
E = hf
f
= 2.09 x 10-18 J/(6.63 x 10-34 J•s)
= 3.16 x 1015 /s
c = f * wlength
wlength = 3.00 x 108 m/s/(3.16
x 1015 /s) = 9.50 x 10-8
m
(b) ni = 4 nf = 2
E = -2.18 x 10-18 J * (1/22 - 1/42)
E = -4.09 x 10-19 J and because E is negative, energy is emitted
E = hf
f
= 4.09 x 10-19 J/(6.63 x 10-34 J•s)
= 6.17 x 1014 /s
c = f * wlength
wlength = 3.00 x 108 m/s/(6.17
x 1014 /s) = 4.87
x 10-7 m
Because this wavelength or frequency falls in the visible portion of the electromagnetic spectrum, visible light is emitted.
(c) ni = 4 nf = 6
E = -2.18 x 10-18 J * (1/62 - 1/42)
E = 7.57 x 10-20 J and because E is positive, energy is absorbed
E = hf
f
= 7.57 x 10-20 J/(6.63 x 10-34 J•s)
= 1.14 x 1014 /s
c = f * wlength
wlength = 3.00 x 108 m/s/(1.14
x 1014 /s) = 2.63 x 10-6
m