Obtain Bohr's quantization condition on the basis of the web nature of an electron.

If an electron moves in a circular orbit of radius R around A nucleus then the circular orbit can be taken to a stationary energy state only, when it contains an integral multiple of de Broglie wavelength,I.e.

          nλ=2πr

         =>n   h/mv=2πr

         =>mvr=hλ/2π

Describe in brief the working of photo-cell.

When high frequency liteforce on the ammeter, photoelectrons are emitted. These are drawn to the collector and a photoelectric current flows in the circuit. The current is proportional to the intensity of incident light.

Define genetic material.

DNA is the genetic material. RNA has been found to be genetic material in TMV,   Φβ bacteriophage etc. DNA is made of a series of nucleotides which in turn form a large number of genes. genes are the bearer of hereditary characters reached chromosome is made up of highly coiled DNA.

Discuss the structure of nucleosome.

Histones are positively charged  which organised to fall a unit of 8 molecular call histone octamer. Negatively charged DNA wrap twice over the octamer forming a structure called nucleosome.

Give the definition of nucleosome.

Nucleosome is a structure formed by wrapping of histone octamer by negatively charged DNA.

What is euchromatin?

Chromatin of nucleus which stain positively with the DNA specific stain indicating the concentration of DNA is called euchromatin.

Define chromatin.

DNA and histone protein together is called chromatin.