Which of the following relations is correct between the time period $(T)$ and the number of orbits $(n)$ for an electron revolving in a Bohr orbit?

In which of the following systems will the radius of the first orbit $(n = 1)$ be minimum?

Consider a hydrogen atom with its electron in the $n^{\text{th}}$ orbital. An electromagnetic radiation of wavelength $90 \ nm$ is used to ionize the atom. If the kinetic energy of the ejected electron is $10.4 \ eV$,then the value of $n$ is $(hc = 1242 \ eV \ nm)$.

An electron in the hydrogen atom jumps from the first excited state to the ground state. What will be the percentage change in the speed of the electron (in $\%$)?

If the de-Broglie wavelength of an electron in the first Bohr orbit is $\lambda$,then the minimum radial distance between the electrons in the first and second Bohr orbits is:

The ionization potential of a hydrogen atom is $13.6 \ eV$. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy $12.1 \ eV$. According to Bohr's theory,the number of spectral lines emitted by the hydrogen atoms will be: