Class 7 Science - KERALA
Light: Shadows and Reflections
The Class 7 Kerala SCERT Science chapter 'Light: Shadows and Reflections' introduces students to the fascinating behavior of light. Learners explore how light travels in a straight line and what happens when it encounters various objects. The chapter details the formation of shadows, explaining opaque, translucent, and transparent materials through simple daily life examples. Furthermore, it covers mirrors, how they form images through reflection, and the left-right reversal known as lateral inversion. This chapter is vital for the board exams as it builds foundational physics concepts tested through diagram-based questions and practical reasoning.
Start Learning FreeKey Concepts
Rectilinear Propagation of Light
Light always travels in a straight line, which is why opaque objects block it to form dark patches called shadows.
Transparent, Translucent, and Opaque Objects
Transparent objects allow light to pass through completely, translucent objects allow partial light, and opaque objects block light entirely.
Shadow Formation
A shadow is formed on a screen when an opaque object blocks the path of light, requiring a light source, an object, and a screen.
Reflection of Light
When light falls on a shiny, polished surface like a plane mirror, it bounces back, changing its direction.
Lateral Inversion
The phenomenon where the right side of an object appears as the left side and vice versa in a mirror image.
Important Formulas
Board Exam Info
In Kerala (SCERT) Class 7 examinations, this chapter typically carries around 6 to 10 marks. Common question types include identifying transparent/opaque materials, drawing ray diagrams or shadow setups, explaining reasons for lateral inversion, and differentiating between real and virtual images or shadows and images.
Frequently Asked Questions
Why is a shadow always black even if the object is colored?
A shadow is simply an absence of light. When an opaque object blocks light, no light reaches that area on the screen, creating a dark patch regardless of the object's color.
What is the difference between an image and a shadow?
An image shows the details, colors, and features of an object (formed by reflection/refraction), whereas a shadow is just a dark outline or silhouette showing only the shape.
Why does the word 'AMBULANCE' written in front look inverted?
Due to lateral inversion in plane mirrors, the left and right sides are reversed, so drivers looking in their rear-view mirrors can read it correctly.
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