Law of diminishing returns is a fundamental concept in economics which states that as the quantity of one input is increased while keeping all other inputs constant, the marginal product of that input will at some point begin to decline. This means that the additional output produced by each additional unit of input will start to decrease, eventually leading to a point where the overall output begins to decline as well.

Applicability of Law of Diminishing Returns:
The law of diminishing returns is applicable in all economic activities after a certain limit. This is because, in any production process, there is a limit to the amount of a particular input that can be used effectively. Beyond that point, the additional input becomes less and less effective, leading to a decline in output. This applies to both agricultural and manufacturing industries, as well as other economic activities such as services and construction.

Examples:
To understand the applicability of the law of diminishing returns, let's take an example of a manufacturing company that produces cars.

Initially, the company can hire more workers and increase their production, leading to higher output. However, after a certain point, each additional worker hired may not be able to produce the same output as the previous worker, leading to a decline in overall output.

Similarly, in agriculture, if a farmer uses too much fertilizer or irrigation, the yield of crops may increase initially. However, beyond a certain point, the additional input may not have the same effect, and may even harm the crops or soil, leading to a decline in overall yield.

Conclusion:
Therefore, it can be concluded that the law of diminishing returns is a fundamental concept in economics, applicable in all economic activities after a certain limit. It highlights the importance of efficient allocation of resources and careful management of inputs to maximize output and productivity.