The value of one Einstein for radiation of wavelength $9000 \ \mathring{A}$ is .............

Two radiations having energies $E_1$ and $E_2$ as $15 \ eV$ and $45 \ eV$ respectively,then the relationship between $\lambda_1$ and $\lambda_2$ will be:

Calculate the wavelength of yellow light having a frequency of $5.09 \times 10^{14} \ Hz$.

The number of the following statements which is/are incorrect is:
$A$. Line emission spectra are used to study the electronic structure.
$B$. The emission spectra of atoms in the gas phase show a continuous spread of wavelength from red to violet.
$C$. An absorption spectrum is like the photographic negative of an emission spectrum.
$D$. The element helium was discovered in the sun by spectroscopic method.

The $Cs^+$ ion imparts a violet color to the flame. How is this related to the emitted radiation?

$\alpha$-rays have