Current amplification factor of a common base configuration is 0.88. The value of base current when the emitter current is  $1mA$ is  $n\times {10}^{-5} A$ then the value of $n$  is 

In a common – base arrangement, the current amplification factor.
 $\alpha =\left(\frac{N_c}{A_K}\right))=\frac{I_c}{I_C};$Given  $\alpha =0.88I_7=\mathrm{lm}$.
Collector current  $I_C=\alpha I_E=0.88\times 1=0.88mA$
Now since  $I_E=I_B+I_C$
base current  ${\mathrm{I}}_B=I_E-l_F=1-0.88=0.12mA$.