Learn ICSE Class 10 Physics Chapter 5 Refraction Through a Lens in simple language. This lesson covers convex lens, concave lens, ray diagrams, lens formula, magnification, power of lens, defects of vision and important numerical problems.
Official ICSE WebsiteThe ICSE Physics syllabus continues to focus heavily on numerical problems, ray diagrams and conceptual understanding from optics chapters. Refraction Through a Lens remains one of the highest scoring chapters in board exams.
A lens is a transparent refracting medium bounded by two surfaces, at least one of which is curved.
A convex lens is thicker at the centre and thinner at the edges. It converges light rays and is also called a converging lens.
A concave lens is thinner at the centre and thicker at the edges. It diverges light rays and is also called a diverging lens.
Where:
Magnification tells how large or small the image is compared to the object.
Power is measured in Dioptre (D).
A person can see nearby objects clearly but distant objects appear blurred. Corrected using a concave lens.
A person can see distant objects clearly but nearby objects appear blurred. Corrected using a convex lens.
If focal length of a lens is 50 cm:
Therefore, the power of the lens is 2 Dioptre.
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A convex lens is thicker at the centre and converges light rays.
The lens formula is: 1/f = 1/v - 1/u
Power of lens is the reciprocal of focal length in metre.
Concave lens is used to correct myopia.
Convex lens is used to correct hypermetropia.