Light: Shadows and Reflections - Class 7 Science (CBSE)
Based on the 2026-27 Class 7 Science syllabus for the NCERT-aligned book Curiosity. Use these notes to understand, observe, explain, and answer in full sentences.
1. Why this chapter matters
Light helps us see, but it also follows patterns. It travels in straight lines, forms shadows when blocked, and reflects from smooth shiny surfaces.
This chapter is not meant for rote learning. Read every idea with an example, then ask: what can I observe, test, draw, measure, or explain?
2. Core ideas
Sources of light
Luminous objects emit light; non-luminous objects are seen when light reflects from them.
Rectilinear propagation
Light travels in straight lines in a uniform medium. This explains shadows and pinhole images.
Reflection
A plane mirror forms an erect image of the same size, at the same distance behind the mirror as the object is in front, with lateral inversion.
3. Key points to remember
- Observation: Record what is actually seen, measured, or compared.
- Fair test: Change one factor and keep other factors the same.
- Conclusion: Use evidence to answer the question.
- Scientific vocabulary: Use precise terms from the chapter.
4. Worked examples
Example 1: Why does an opaque object form a shadow?
It blocks light, creating a dark region behind it.
Example 2: Why can we see the Moon?
The Moon reflects sunlight; it does not produce its own light.
Example 3: What is lateral inversion?
In a mirror image, left and right appear interchanged.
Example 4: Why does a pinhole camera form an inverted image?
Light travels in straight lines through the small hole.
5. Activity and observation
Use three cards with holes. A candle flame is visible only when the holes are aligned, showing that light travels in a straight line.
Write the activity in this format:
- Aim: What are you trying to find out?
- Materials: What did you use?
- Procedure: What steps did you follow?
- Observation: What did you see or measure?
- Conclusion: What scientific idea does it prove?
6. Common mistakes
- Writing only definitions without examples.
- Drawing diagrams without labels.
- Confusing observation with conclusion.
- Ignoring units in speed, time, distance, temperature, or measurement questions.
- Giving unsafe suggestions for experiments instead of classroom-safe methods.
7. Practice set
- Define the main idea of Light: Shadows and Reflections.
- Write two key terms from this chapter and explain them.
- Describe one activity that proves an idea from this chapter.
- Give one real-life application of light sources.
- Write one difference-based question from this chapter.
- How can you make your answer more scientific?
8. Answer key
-
Define the main idea of Light: Shadows and Reflections. Answer: Light helps us see, but it also follows patterns. It travels in straight lines, forms shadows when blocked, and reflects from smooth shiny surfaces.
-
Write two key terms from this chapter and explain them. Answer: light sources and straight-line travel are central terms. Define each with one example from daily life.
-
Describe one activity that proves an idea from this chapter. Answer: Use three cards with holes. A candle flame is visible only when the holes are aligned, showing that light travels in a straight line.
-
Give one real-life application of light sources. Answer: Use the chapter idea to explain a daily event, then name the observation that supports your answer.
-
Write one difference-based question from this chapter. Answer: Compare two related ideas, such as Sources of light and Rectilinear propagation, using meaning and example.
-
How can you make your answer more scientific? Answer: Use observation, correct vocabulary, labelled diagrams or tables, and a clear reason.
9. Quick revision
- Main themes: light sources, straight-line travel, transparent materials, shadows, reflection, plane mirror.
- Learn definitions with examples.
- Practise one diagram, table, or activity.
- Revise the worked examples.
- Write answers using cause, evidence, and conclusion.
