Generate a full, in-depth guide for students on the 'Feynman Technique.' The guide must be written in a clear and encouraging tone. It should include detailed sections on: 1. The philosophy behind the technique: 'If you can't explain it simply, you don't understand it well enough.' 2. A detailed, step-by-step walkthrough of the four steps (Choose a concept, Teach it to a child, Identify gaps, Review and simplify). 3. A practical example of applying the technique to a complex topic like photosynthesis. 4. How to use this method for exam preparation. Please include a supportive disclaimer.