Question

A. What is the minimum wavelength of x-rays?

Knowns: 45 KeV at a tungsten target

B. an electron in hydrogen goes from n = 5 to the n = 3 energy level.

What wavelength of light is emitted?

Answer 1

A.

Energy of electrons,E=45keV=451.610-19 J

Also

E=hc/

So,minimum wavelength of X-ray is

=hc/E=(6.6310-343108)/(451.610-19 )=2.7610-8 m

B.

Energy of transition from one state to other in H-atom is

E=-13.6eV[1/(n1)2-1/(n2)2]

Also

E=hc/

n1=5 and n2=3

so

E=-13.6eV[1/(5)2-1/(3)2]=-13.61.610-19[1/(5)2-1/(3)2]=1.5510-19 J

So

Wavelength of emitted light is

=hc/E=(6.6310-343108)/(1.5510-19 )=1.2910-6 m