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 photoelectric effect shows:

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

$\alpha$-rays have

The number of incorrect statement/s about the black body from the following is $........$.
$(A)$ Emit or absorb energy in the form of electromagnetic radiation
$(B)$ Frequency distribution of the emitted radiation depends on temperature
$(C)$ At a given temperature,intensity vs frequency curve passes through a maximum value
$(D)$ The maximum of the intensity vs frequency curve is at a higher frequency at higher temperature compared to that at lower temperature

What is light?