The graph that depicts Einstein's photoelectric effect for a monochromatic source of frequency above the threshold frequency is

If in Bohr's model,for a unielectronic atom,the time period of revolution is represented as $T_{n,Z}$ where $n$ represents the shell number and $Z$ represents the atomic number,then the value of $T_{1,2} : T_{2,1}$ will be

What is the number of waves formed by an electron in the $5^{th}$ Bohr orbit of a hydrogen atom?

Photon of the maximum frequency will be absorbed in the transition (for $H$ atom):

What transition in $He^{+}$ ion shall have the same wave number as the first line in Balmer series of hydrogen atom?

The electron in the $n^{th}$ orbit of $Li^{2+}$ is excited to $(n+1)$ orbit using the radiation of energy $1.47 \times 10^{-17} \ J$. The value of $n$ is $....$. Given $R_H = 2.18 \times 10^{-18} \ J$.