Final answer:
When solar panels are used to gather energy to heat a swimming pool, the type of energy transformation occurring is radiant to thermal energy. Solar panels contain photovoltaic cells that directly convert sunlight, which is radiant energy, into electrical energy. This electrical energy can then be used to heat water, in this case, for a swimming pool. The actual transformation in a solar thermal system involves the solar radiation being absorbed and converted directly into thermal energy to heat the pool water.
Step-by-step explanation:
The type of energy transformation occurring when solar panels are used to heat a swimming pool is d. Radiant to thermal.
Solar panels, also known as photovoltaic cells, convert solar energy from the sun into electrical energy. This electrical energy is then used to power a heating system, which transforms the electrical energy into thermal energy to heat the water in the pool.
Therefore, the correct answer is d. Radiant to thermal.