Question

A observer on the planet observes two spaceships are moving toward each other. If one traveling at a speed of $\frac{c}{6}$ and the other at a speed of $\frac{c}{3}$. The faster spaceship emits a radar pulse directed toward second spaceship. Calculate the speed of radar pulse as measured by observer on the planet.

• A. $\frac{c}{2}$
• B. $\frac{5c}{6}$
• C. $c$
• D. $\frac{7c}{2}$
• E. $\frac{3c}{2}$

Answer 1

Answer: (C)

$c$

According to the principle of Relativity, the speed of all light waves as observed by an observer in all inertial frames is constant and equal to $c$.
Thus the speed of radar pulse observed by observers on either spaceship and on the planet is same, $c$.