Introduction:
The value of acceleration due to gravity, denoted by 'g', decreases as the depth increases. This phenomenon can be explained by considering the following factors:

Distribution of Mass:
The Earth is not a perfectly uniform sphere; it has a non-uniform distribution of mass. The mass of the Earth is concentrated towards its center, and as we move away from the surface towards the core, the mass increases. This non-uniform distribution of mass affects the gravitational pull and leads to a decrease in the value of 'g' with increasing depth.

Distance from the Center:
The gravitational force experienced by an object is directly proportional to the mass of the object and inversely proportional to the square of the distance between the object and the center of mass. As we descend deeper into the Earth, the distance from the center decreases. Therefore, the gravitational force acting on an object decreases due to the reduced distance from the center of the Earth.

Shell Theorem:
The Shell Theorem states that inside a hollow, spherically symmetric shell of matter, the gravitational force experienced by a particle is zero. As we move deeper into the Earth, we can consider the layers above as shell-like structures. The gravitational force experienced by an object due to the layers above it cancels out, resulting in a decrease in the net gravitational force and hence a decrease in 'g'.

Increasing Mass Above:
As we move deeper into the Earth, there is an increasing amount of mass above the object. According to Newton's Law of Universal Gravitation, the gravitational force experienced by an object is directly proportional to the mass of the attracting object. The increased mass above the object leads to a stronger gravitational force pulling it upwards, thereby reducing the effective gravitational force experienced by the object and causing a decrease in 'g'.

Conclusion:
In conclusion, the decrease in the value of 'g' as the depth increases can be attributed to the non-uniform distribution of mass, the reduced distance from the center of the Earth, the cancellation of gravitational forces due to shell-like structures, and the increasing mass above the object. These factors collectively contribute to the variation in 'g' with depth.

value of g decreases with depth because as we go downwards from earth surface the effective mass of earth decreases which is directly proportional to value of g