When ultraviolet light of wave length of 100nm shines on particular metal in vac

Question

When ultraviolet light of wave length of 100nm shines on particular metal in vacuum the maximum kinetic energy of injected photo electrons is 10.o ev longer wavelengths produce less energetic electrons above what threshold wave length would no photoelectrons be detected Bohr's theory of hydrogen-like atoms predicts energy levels E = -13.6 7.2/nJ eV where Z is the atomic number. What wavelength would be produced by the n=4 to n=2 transition in Be, for which Z=4 With what force will two protons repel each other if they are 10^-10 m apart Fundamental Constants e=1.6xlO,9C h=6.6x 10341 c=3.0 x 10Bm/s k= 9.0 xl09Nm2C2

Explanation / Answer

14)

hc/ = + E

h – plank’s constant 6.63 x 10-34 J s

c – speed of light 2.99 x 108 m/s

– wavelength of incident photon

– photo electric work function

E - maximum energy of emitted photon

6.63 x 10-34 x 2.99 x 108 / 100 x 10-9 m = – 10 ev

19.81174 x 10-19 J = – 16.02 x 10-19 J

= 3.79174 x 10-19 J

This is the minimum energy required to remove a electron from the orbit for the given metal

So the maximum wavelength

= hc/

= 6.63 x 10-34 x 2.99 x 108 / 3.79174 x 10-19

= 522.8 x 10-9 m

16)

F = ke2/ (1 x 10-10)2

= 9 x 109 x ( 1.6 x 10-19)2 / 10-20

= 23.04 x 10-9 N

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