When $X$-rays are incident on an object in a dark room,they will appear as ........

The potential difference applied to an $X-$ray tube is increased. As a result,in the emitted radiation:

$A$ charged gold leaf electroscope has its leaves apart by a certain amount with enclosed air. When the electroscope is subjected to $X$-rays,then the leaves

When $0.50\; \mathring{A}$ $X$-rays strike a material,the photoelectrons from the $K$-shell are observed to move in a circle of radius $23\; mm$ in a magnetic field of $2 \times 10^{-2}\; T$ acting perpendicularly to the direction of emission of photoelectrons. The binding energy of $K$-shell electrons is $..........\; keV$.

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

Frequency of the $K_{\alpha}$ $X$-ray for the element calcium $(Ca, Z = 20)$ is $8.95 \times 10^{17} \ Hz$. The frequency of the $K_{\alpha}$ $X$-ray for the element cadmium $(Cd, Z = 48)$ will be: