At the time of a total solar eclipse,the spectrum of solar radiation would be:

If the voltage of an $X$-ray tube is doubled,the intensity of $X$-rays will become

The $X$-rays produced by a Coolidge tube consist of . . . . .

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

The wavelength of the ${K_{\alpha}}$ line for an element of atomic number $43$ is $\lambda$. Then the wavelength of the ${K_{\alpha}}$ line for an element of atomic number $29$ is:

$A$ metal target with atomic number $Z=46$ is bombarded with a high-energy electron beam. The emission of $X$-rays from the target is analyzed. The ratio $r$ of the wavelengths of the $K_\alpha$-line and the cut-off wavelength is found to be $r=2$. If the same electron beam bombards another metal target with $Z=41$,the value of $r$ will be