Given below in the left column are different modes of communication using the kinds of waves given in the right column.
$$\begin{array}{|l|l|l|l|}\hline (1) & \text{Optical fibre communication} & (P) & \text{Ultrasound} \\ \hline (2) & \text{Radar} & (Q) & \text{Infrared light} \\ \hline (3) & \text{Sonar} & (R) & \text{Microwaves} \\ \hline (4) & \text{Mobile phones} & (S) & \text{Radio waves} \\ \hline \end{array}$$
From the options given below, find the most appropriate match between entries in the left and the right column.
Answer: (A) 1 – Q, 2 – S, 3 – P, 4 – R
Optical fibres carry infrared light (1 – Q). Sonar uses ultrasound (3 – P). Mobile phones work with microwaves (4 – R), and radar is matched with radio waves (2 – S).
Only option (1) has these pairings.
Solution by Sreeraj P, M.Sc Physics