JEE Advanced
Physics
Electromagnetic Waves
2020
JEE Advanced 2020 (Paper 2)
JEE Advanced Physics Question (2020) — Solution
Question
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
- A. the cut-off wavelength will reduce to half, and the wavelengths of the characteristic X-rays will remain the same
- B. the cut-off wavelength as well as the wavelengths of the characteristic X-rays will remain the same
- C. the cut-off wavelength will reduce to half, and the intensities of all the X-rays will decrease
- D. the cut-off wavelength will become two times larger, and the intensity of all the X-rays will decrease
Answer
C. the cut-off wavelength will reduce to half, and the intensities of all the X-rays will decrease
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.
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