Define rectilinear propagation of light​

Electromagnetic waves to travel in a straight line. Light only deviates from a straight line when the medium it is travelling through changes density. This is called refraction. Light does not deviate when travelling through a homogeneous medium, which has the same refractive index throughout. Wikipe

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

answer: a) y=-8x+5

a) m= -8

b) m= -2

c) m= 7

d) m= 6