Is it essential that each incident photos should eject a photoelecton?Explain.

If lamda_o and lamda be the threshold wavelength and wavelength of incident light , the velocity of photoelectron ejected from the metal surface is :

The question given below consist of an assertion (A) and a reason ( R). Use the following key to choose the appropriate answer to these questions from the codes (a), (b), ( c) and (d) given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is NOT the correct explanation of A. (c) A is true but R is false. (d) A is false and R is also false. Assertion: Kinetic energy of photo electrons emitted by a photosensitive surface depends upon the intensity of incident photon. Reason: The ejection of electrons from metallic surface is possible with frequency of incident photon below the threshold frequency.

Magnetic lines of force should better be called as field lines. Explain.

For a group photograph, 3 boys and 2 girls stand in a line in all possible ways. How many photos could be taken if each photo corresponds to each such arrangement ?

To hear beats,it is essential to have two frequencies very close to each other.Why?

Given instructions same as in chapter 1. Assertion: For photoelectric effect to take place, the frequency of incident of incident radiations should be more than threshold frequency of a given metal Reason: 1/2 mv^2=h(v-v_0) .

Amino acids can be classified into essential amino acids and non-essential amino acid. Write one example each for essential and non- essential amino-acids.