Answer:
(C) 21.6 pm
Explanation:
[tex]\lambda_i[/tex]= Initial wavelength = 18 pm
[tex]\lambda_f[/tex]= Final wavelength
mc² = Eloectron rest mass = 0.511 MeV
h = Planck's constant
c = Speed of light
hc = 1240 eV nm
[tex]\Delta \lambda=\lambda_f-\lambda_i=\frac{hc}{mc^2}(1-cos\theta)\\\Rightarrow \lambda_f-18=\frac{1240}{0.511}(1-cos120)\\\Rightarrow \lambda_f-18=3.63\\\Rightarrow \lambda_f=3.63+18\\\Rightarrow \lambda_f=21.63[/tex]
∴ Wavelength of the scattered photon is 21.63 pm
