hii do we consider sign conventions while solving numericals using lens formula for example while calculating power of lens

When you need to gauge the separation in the inverse side of the episode beam (we generally measure the separation from the optical focus) at that point it is taken as negative separation. 

When you measure the separation toward the occurrence beam it is certain separation. 

Statures measured over the chief hub is certain and underneath the vital hub is negative. 

P=1/central length 

As per our sign tradition central length of a curved focal point is sure. Henceforth the power will be certain. 

central length of sunken focal point is negative. Subsequently the power is additionally negative. 

Cheers!!

Regards,

Vikas (B. Tech. 4^th year
Thapar University)