The potential difference between the target and the cathode of an X-ray tube is 50 kV. The current in the tube is 20 mA. Only 1% of the total energy is emitted as X-rays. (Take: hc = 1240 eV nm)
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Question

The potential difference between the target and the cathode of an X-ray tube is 50 kV. The current in the tube is 20 mA. Only 1% of the total energy is emitted as X-rays. (Take: hc = 1240 eV nm)

G1 Physics · Accepted Answer

Electrical input power is VI=50 kV×20 mA=1000 W. Maximum photon energy is 50 keV, so νₘₐₓ≈1.2×10¹⁹ Hz (A). Only 1% becomes X-rays, so heat≈990 W, not 900 W (B false). λₘᵢₙ=1240/50000≈0.0248 nm, so 0.2 nm is possible (C). Electron rate I/e≈1.25×10¹⁷ s⁻¹ (D). Correct: A, C, D.