Answer:
350 J
Step-by-step explanation:
The law of conservation of energy states that energy can neither be created nor destroyed but can only be converted from one form to another. This means that in a system, energy is not lost.
In this question, an unlit match contains approximately 1,000 J of chemical energy. When lit, thermal and light energy are emitted i.e. it gets converted to light and heat energy. If the thermal energy emitted was measured to be 400J, and the remaining match still contains 250J of chemical energy, then:
The amount of light energy emitted will be:
Total chemical energy (1000J) - {Remaining chemical energy (250J) + emitted thermal energy (400J)}
= 1000 - (400 + 250)
= 1000 - 650
= 350
Hence, the amount of light energy emitted is 350J
Note that, the amount of energy converted (thermal and light) and remaining chemical energy still equates the total chemical energy in the match.