Answer:
0.5 m
Explanation:
Two charges each of magnitude q
Let the third charge is Q is placed at a distance x from the origin so that the charge is in equilibrium.
The force on Q due to q at origin is balanced by the charge on Q due to the charge q placed at x = 1 m.
So,

1 - x = x
1 = 2x
x = 0.5 m
Thus, the third charge is placed at x = 0.5 m .
A) seismic waves
b) sound waves
sound waves are traveling vibrations of particles in media (air, water, metal, etc) so they can’t travel through empty space (vacuums) because there are no atoms or molecules to vibrate.
seismic waves are mechanical waves and require a medium for propagation, hence, they cannot travel through a vacuum.
hope this helps :)
Whenever light goes from transparent to another medium or from rarer to denser medium or vice versa, it's speed changes and hence light bends.