In an X -ray tube, electrons emitted from a filament (cathode) carrying current I hit a target (anode) at a…

In an X-ray tube, electrons emitted from a filament (cathode) carrying current I hit a target (anode) at a distance d from the cathode. The target is kept at a potential V higher than the cathode resulting in emission of continuous and characteristic X-rays. If the filament current I is decreased to I2, the potential difference V is increased to 2V, and the separation distance d is reduced to d2, then
  1. the cut-off wavelength will reduce to half, and the wavelengths of the characteristic X-rays will remain the same
  2. the cut-off wavelength as well as the wavelengths of the characteristic X-rays will remain the same
  3. the cut-off wavelength will reduce to half, and the intensities of all the X-rays will decrease
  4. the cut-off wavelength will become two times larger, and the intensity of all the X-rays will decrease

Solution

Cut off wavelength λC∝1V

So, cut-off wavelength becomes half.

Characteristic x-ray depends on target atomic number, so it remains same.

On decreasing filament current number of electron decrease, so intensity of X -ray decreases.

Asked in: JEE Advanced 2020 (Paper 2)

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