In the visible spectrum,which color,violet or red,undergoes greater refraction? Why?

Calculate the wavenumber $\bar{v}$ in $cm^{-1}$ for yellow radiation having a wavelength of $5800 \ \mathring{A}$.

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

Choose the correct statements in reference to the photoelectric effect. $(i)$ There is no time lag between the striking of light and ejection of electrons from the metal surface. $(ii)$ The number of electrons ejected is independent of the intensity of light. $(iii)$ The elements $K$, $Rb$ and $Cs$ can show photoelectric effect when exposed to the beam of light.

Identify the correct statements from the following:
$I$) Isotopes of an element show different chemical behaviour
$II$) Lyman series of lines of hydrogen spectrum appear in $UV$ region
$III$) The oscillating electric and magnetic field components of electromagnetic radiation are perpendicular to each other and both are perpendicular to the direction of propagation of radiation

What is an emission spectrum?