Question

The minimum thickness of film which will strongly reflect the normally incident light of $\lambda =600$nm, the R.I of material of film is $1.25$.

• A. $120$nm
• B. $100$nm
• C. $110$nm
• D. $90$nm

Answer 1

The correct option is A $120$nm

$2\mu t=\frac{\lambda }{2}$

$t=\frac{6\times {10}^{-7}}{4\times 1.25}$

$=1.2\times {10}^{-7}m$