Question

What will be the amount of energy available to the organisms of the $2^{\text{nd}}$ trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules?

Answer 1

According to 10% law of energy, whatever enery an organism have in a food chain only 10 % of it is tranferred to the next level and 90% of energy is always used up by the organism itself for daily works, body heat ,reproduction,etc.
So the energy available at the $2^{\text{nd}}$ trophic level of a food chain is 1000 J.