JEE Advanced2020PhysicsElectromagnetic WavesActual
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 I 2 , the potential difference V is increased to 2 V , and the separation distance d is reduced to d 2 , then
Options
- Athe cut-off wavelength will reduce to half, and the wavelengths of the characteristic X-rays will remain the s
- Bthe cut-off wavelength as well as the wavelengths of the characteristic X-rays will remain the same
- Cthe cut-off wavelength will reduce to half, and the intensities of all the X-rays will decrease
- Dthe cut-off wavelength will become two times larger, and the intensity of all the X-rays will decrease
Correct answer
A. the cut-off wavelength will reduce to half, and the wavelengths of the characteristic X-rays will remain the s
Step-by-step solution
Cut off wavelength λ C ∝ 1 V 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.