Class 8 Science - WEST-BENGAL
Light: Mirrors and Lenses
In the Chapter 'Light: Mirrors and Lenses' from the Class 8 West Bengal Board (WBBSE) science syllabus, students explore the fascinating behavior of light. You will learn about the laws of reflection, regular and diffused reflection, and how plane and spherical mirrors (concave and convex) form different types of images. The chapter also introduces refraction through lenses, dispersion of light through prisms, and the basic structure of the human eye. Mastering this chapter is crucial for your board exams as it forms the foundational optics concepts required for higher classes and frequently features in numerical and diagram-based questions.
Start Learning FreeKey Concepts
Laws of Reflection
The angle of incidence is always equal to the angle of reflection, and the incident ray, reflected ray, and the normal at the point of incidence all lie in the same plane.
Real and Virtual Images
A real image can be obtained on a screen and is formed by actual intersection of light rays, whereas a virtual image cannot be caught on a screen and appears to diverge from a point.
Spherical Mirrors
Concave mirrors converge light rays and can form real or virtual images, while convex mirrors diverge light rays and always form diminished, virtual images.
Refraction of Light
The bending of light when it passes obliquely from one transparent medium into another due to a change in its speed is called refraction.
Dispersion of Light
The splitting of white light into its seven constituent colors (VIBGYOR) when passing through a glass prism is known as dispersion.
Important Formulas
Board Exam Info
In the West Bengal Board (WBBSE) Class 8 final science examinations, this chapter typically carries around 6 to 10 marks. Common question types include ray diagrams for image formation by mirrors and lenses, definitions of laws of reflection and refraction, numericals based on angles, and short-answer questions about the human eye and dispersion.
Frequently Asked Questions
Because convex mirrors curve outwards, they diverge the parallel rays of light falling on them, creating a smaller, virtual image behind the mirror, which is why they are used as rear-view mirrors in vehicles.
Because convex mirrors curve outwards, they diverge incoming light rays, always producing a virtual, erect, and diminished image which allows a wider field of view.
What is the difference between regular and diffused reflection?
Regular reflection happens on smooth surfaces like mirrors where parallel rays reflect in a single direction. Diffused reflection happens on rough surfaces where parallel rays scatter in different directions.
Can a virtual image be photographed?
Yes, a virtual image can be photographed because the camera lens refracts the virtual rays diverging from the mirror/lens and focuses them into a real image on the camera's sensor or film.
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