1. why alkali metals are most suitable as photosensitive surfaces?

2. can we get photoemission with an intense beam of radiowaves?

3. is photoelectric emission at all frequencies?

4. what is minimum angular momentum of electron in hydrogen atom?

5. which quantity of the orbiting electron has same dimension as that of h?

6. how many spectral lines are possible in hydrogen spectrum?

7. which hydrogen spectral series is found first?

8. which parameter is same for all photons in laser tube?

9. which microscope will you use to study surface structure of different materials?

Photoelectric effect is the phenomenon by which the electrons are ejected from the surface of the metal when a radiation of suitable frequency is used. 

 1)  Alkali metals have only one electron in there valence shell ,there electronic configuration is 3s¹ . They have very low ionization energy so it will be easy to eject the electron from the alkali metals .Thus they are suitable for this  effect.

2) For the ejection of electron a radiation of high energy is used that is of low wavelength but radio waves are of larger wavelength it means of  low energy . Thus radio waves are not suitable for this purpose.

3) Photoelectric effect takes place only when a light of suitable frequency is used that is a frequency greater than the threshold frequency is used , then only ejection of electron takes place . Thus this effect can not takes place at all the frequencies . 

4) The angular momentum can be calculated by the formula √l(l+1) h/2π, which you will study at your higher grade. So for the hydrogen atom l=0 , because it has 1s¹ electronic configuration and for s orbital the value of l=0 . Thus by putting this value in the formula we get zero value of angular momentum.

6) There are a large number of lines that occur in the hydrogen spectrum corresponding to the different value of the frequencies .

Due to the lack of time ,i am not able to answer all of your question. Please try to solve yourself if in case you face any problem ,please let me know so that i can provide you valuable help.