Question

Two coherent monochromatic light beams of amplitude $3$ and $5$ units are superposed. The maximum and minimum possible intensities in the resulting beams are in the ratio

• A. 4 : 2
• B. 16 : 1
• C. 8 : 2
• D. 18 : 2

Answer 1

Answer: (B)

It is given that the amplitudes $A_1$ and $A_2$ are in the ratio $\frac{A_1}{A_2}=\frac{3}{5}$
$\therefore$ After superposition the maximum and minimum intensities will be in the ratio
$\frac{I_{max}}{I_{min}}=\frac{{\left(A_1+A_2\right)}^2}{{\left(A_1-A_2\right)}^2}$
$=\frac{{\left(3+5\right)}^2}{{\left(3-5\right)}^2}$
$=\frac{8^2}{{\left(-2\right)}^2}=\frac{64}{4}=\frac{16}{1}$