$A$ hypothetical electromagnetic wave is shown below. The frequency of the wave is $x \times 10^{19} \ Hz$. $x =$ . . . . (nearest integer)

The radiation is emitted when a hydrogen atom goes from a high energy state to a lower energy state. The wavelength of one line in the visible region of the atomic spectrum of hydrogen is $6.5 \times 10^{-7} \, m$. The energy difference between the two states is:

$a$,$b$,$c$,$d$ are electromagnetic radiations. Frequencies of $a$,$b$ are $3 \times 10^{15} \ Hz$,$2 \times 10^{14} \ Hz$,respectively,whereas wavelengths of $c$,$d$ are $400 \ nm$,$750 \ nm$,respectively. The increasing order of their energies is

Chlorophyll present in green leaves of plants absorbs light at $4.620 \times 10^{14} \ Hz$. Calculate the wavelength of radiation in nanometer. Which part of the electromagnetic spectrum does it belong to?

The ....... series is observed in the visible region of the hydrogen spectrum.

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.