what is initial lag phase,logarithmic or exponential phase,and stationary phase..... Give some details about all

During lag phase, bacteria adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide. 

Exponential phase (sometimes called the log phase or the logarithmic phase) is a period characterized by cell doubling.

The "stationary phase" is due to a growth-limiting factor; this is mostly depletion of a nutrient, and/or the formation of inhibitory products such as organic acids. An awkward but unfortunately wide-spread explanation is that the stationary phase results from a situation in which growth rate and death rate have the same values.

At death phase, bacteria run out of nutrients and die. This basic batch culture growth model draws out and emphasizes aspects of bacterial growth which may differ from the growth of macrofauna. It emphasizes clonality, asexual binary division, the short development time relative to replication itself, the seemingly low death rate, the need to move from a dormant state to a reproductive state or to condition the media, and finally, the tendency of lab adapted strains to exhaust their nutrients.