2.17 describe the process of photosynthesis and understand its importance in the conversion of light energy to chemical energy

Photosynthesis is the process in which plants use energy from the sunlight to convert carbon dioxide and water into molecules needed for growth. It uses light energy (from the sun) to create chemical energy (glucose) - this conserves the energy from the sun. The energy is then passed through the food chain which is why plants are called producers; they produce the chemical energy.

It works like this...

Light energy is absorbed by the green chemical chlorophyll. This energy allows the production of glucose by the reaction between carbon dioxide and water. 

A bi-product of photosynthesis is oxygen, which is excreted out of the plant via the stomata.