The energy of a photon is $3 \times 10^{-12} \ erg$. What is its wavelength in $nm$? $(h = 6.62 \times 10^{-27} \ erg \cdot s; \ c = 3 \times 10^{10} \ cm/s)$

If the wavelength of the first line of the Balmer series is $656.1 \ nm$,then the wavelength of the second line of this series will be ............. $nm$.

As we move away from the nucleus,the energy of the electron

What is the radius of Bohr's fifth orbit for $B^{+4}$ in $\mathring{A}$ (in $.645$)?

$A$ bulb emits light of wavelength $4500 \ \mathring{A}$. The bulb is rated at $150 \ W$ and $8 \ \%$ of the energy is emitted as light. What is the number of photons emitted by the bulb in $1 \ s$?

The time taken for an electron to complete one revolution in Bohr orbit of hydrogen atom is