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Question
The X-ray coming from a Coolidge tube has a cutoff wavelength of 80 pm. Find the kinetic energy of the electrons hitting the target.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Solution
Given:-
Cutoff wavelength of the Coolidge tube, `lambda = 80 "pm"`
Energy of the electron hitting the target (E) is given by
`E = (hc)/lambda`
Here,
h = Planck's constant
c = Speed of light
λ = Wavelength of light
`therefore E = (1242 "eV"-"nm")/(80 xx 10^-3)`
`⇒ E = (1242 xx 10^-9 "eV")/(80 xx 10^-12)`
`⇒ E = 15.525 xx 10^3 "eV" ≈ 15.5 "keV"`
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