Assertion: $X-$rays travel with the speed of light.
Reason: $X-$rays are electromagnetic rays.

$X$-rays are:

Calculate the wavelength of the $K_{\alpha}$ line for $Z=31$, given $a=5 \times 10^7 \text{ Hz}^{1/2}$ for a characteristic $X$-ray spectrum.

The minimum wavelength of $X$-rays produced by electrons accelerated by a potential difference of $V$ volts is equal to:

An $X$-ray tube operates at $30 \ kV$. What is the minimum wavelength emitted in $\mathring{A}$? (Given: $h = 6.6 \times 10^{-34} \ J \cdot s$,$e = 1.6 \times 10^{-19} \ C$,$c = 3 \times 10^8 \ m/s$)

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 the emission of continuous and characteristic $X$-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 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.