The electron is

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 greater the energy of a photon,the

Assuming that the incident radiation is capable of ejecting photoelectrons from all the given metals,the lowest kinetic energy of the ejected photoelectron is observed with which of the given metals?

Calculate the energy of one mole of photons of radiation whose frequency is $5 \times 10^{14} \ Hz$.

Yellow light emitted from a sodium lamp has a wavelength $(\lambda)$ of $580 \,nm$. Calculate the frequency $(v)$ and wave number $(\bar{v})$ of the yellow light.