Lesson plan complexity depends on the age and knowledge level of the students. Write the lesson plan based off the previous lessons that have set the foundation. If the students are more advanced, try expanding on their current knowledge of the topic.
Follow the typical layout of a lesson plan, keeping in mind that students tend to like hands-on and interactive activities and retain more of the information stemming from these types of lessons. Especially in science, students expect to have more interesting ways to learn than from a simple textbook reading and a worksheet.
If the students are younger, explain light in a basic way that younger, less knowledgeable students can understand. Help students identify sources of light for themselves. For example, have young students draw various light sources, such as the sun or a flashlight. Help the students categorize their drawings into natural and artificial light sources.
For more advanced students, start by asking them to identify sources of light around the classroom. From there, move on to the reasons that these objects are producing light, such as the science behind light bulbs, the moon and the sun, and explain why some light sources are necessary for life to survive.