Q54 / 66 · JEE Advanced 2007 (Paper 1) · Physics

Statement I If the accelerating potential in an X-ray tube is increased, the wavelengths of the characteristic $X$-rays do not change. Statement II When an electron beam strikes the target in an X-ray tube, part of the kinetic energy is converted into X-ray energy.

  • A
    Statement I is true, Statement II is true; Statement II is a correct explanation for Statement I
  • Correct answer
    B
    Statement I is true, Statement II is true; Statement II is NOT a correct explanation for Statement I
  • C
    Statement I is true, Statement II is false
  • D
    Statement I is false, Statement II is true

Solution

Cut-off wavelength depends on the accelerating voltage, not the characteristic $\mathrm{X}$-rays. Further approximately $2 \%$ kinetic energy of the electrons is utilised in producing X-rays. Rest $98 \%$ is lost in heat. $\therefore$ Option (b) is correct.

Hence, the correct answer is option: 'B'.

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