RADAR Method for Measuring Length

The RADAR method is used to measure length (distance). RADAR stands for Radio Detection and Ranging.

How it works:

• RADAR systems emit radio waves towards an object.
• The time taken for the waves to travel to the object and reflect back is measured.
• Using the known speed of radio waves (approximately the speed of light, $c$), the distance ($d$) can be calculated with the formula:

  $d = \frac{c \times t}{2}$

  where $t$ is the total time for the round trip. This calculation directly gives the length or distance to the object.

Why Other Methods Are Unsuitable for Length Measurement

• Dimensional method: This involves dimensional analysis, relating physical quantities, not directly measuring length.
• Pendulum method: Primarily used for measuring time periods or acceleration due to gravity, not length directly.
• Angular method: Measures angles. While angles can be used in techniques like triangulation to determine distances, it's not a direct method for measuring linear length itself in the way RADAR is.

Therefore, the RADAR method is the correct choice for measuring length among the given options.