Q: 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 characteristics X-rays . If the filament current I is decreased to I/2 , the potential difference V is increased to 2V ,and the separation distance d is reduced to d/2 then
(a) the cut-off wavelength will reduce to half and the wavelength of the characteristics X-rays will remain the same
(b) the cut-off wavelength as well as the wavelength of the characteristics 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-ray will decrease
Click to See Solution :
Sol: $\lambda \propto \frac{1}{V}$
So when V double , then cut-off wavelength becomes half . Characteristics does not depend on voltage . When I is halved then intensity will decrease