Explanation:
In train's rest frame, the speed of photon is
and the proper length of the train is
. The time taken by the photon to cross the train is 
In ground frame, the speed of the photon is given as follows:


The speed of light or photon remains same in every frame of reference.
Now, the speed of train is very less as compared to the speed of photon so that
So that, 
The length contraction in the ground frame is given as follows:


Time taken by the photon to travel the length of the train in ground frame is .
A quantity which have both magnitude and direction is know as vector quantity.
Resultant vector is 6.81 m south east.
Triangle law of vector addition is when two vectors are represented as two sides of the triangle with the order of magnitude and direction, then the third side of the triangle represents the magnitude and direction of the resultant vector.
Since, vector K is 3.0 m north and vector L is 8.6 m southeast
So, angle between vectors K and L is,
90+45 = 135 degree
Resultant vector, 

So, Resultant vector R is 6.81 m with direction of southeast.
Learn more:
brainly.com/question/19791435
A. Oscillating magnetic fields are parallel to oscillating electric fields, which are perpendicular to the direction of wave motion.
Answer:
pretty sure its A
Explanation:
please give brainliest if i'm correct