A monochromatic light is one that 

Bifocal lens is used to correct the eye defect of 

A force of 10N extends a spring of natural length 1m by 0.02m, calculate the length of the spring when the applied force is 40N.

Infra-red thermometers work by detecting the 

The efficiency of a cell with internal resistance of 2\(\Omega\) supply current to a 6\(\Omega\) resistor is