An X-ray pulse of wavelength 4.9Å is sent through a section of Wilson cloud chamber containing a super saturated gas, and tracks of photoelectrons ejected from the gaseous atom are observed. Two groups of tracks of length 1.40cm and 2.02 cm are noted. If the range-energy relation for cloud chamber is given by `R=alphaE`, with `alpha=1cm//keV`, obtain the binding energies of two levels from which electrons are emitted. Given `h=6.63xx10^(-34)Js , e=1.6xx10^(-19)C`.

Options

A. 0.52 KeV
B. 0.75 eV
C. 0.52 eV
D. 0.75 keV

Answer

A

Explanation

Binding energy `(phi_0) = (hc)/lamda -E`
`E =R/alpha ` Here `lamda = 4.9 xx10^(-10)m`
`E_1=R_1/(alpha)=(1.40)/1 =1.40 KeV`
`E_2=R_2/(alpha)=(2.02)/1 =2.02 KeV`
Energy of incident photon
`(hc)/lamda = (6.63 xx10^(-34) xx3 xx10^8)/(4.9 xx10^(-10)) =2.54 keV`
`(phi_0)_1 = 2.54 -1.40 = 1.14 KeV`
and `(phi_0)_2 = 2.54 -2.02 = 0.52 KeV`