Q1
A magnifying glass uses a:
Aconvex lens
Bconcave lens
Cplane mirror
Dconcave mirror
CBSEClass 10 (CBSE)ScienceCh 9 · Topic 2
Refraction by Lenses
Learning image formation by convex and concave lenses.
Core concept
The power of a lens (P = 1/f, with f in metres) is measured in dioptres (D), indicating how strongly the lens converges or diverges light — a convex lens has positive power, a concave lens has negative power. A combination of lenses, as used in a camera, microscope, or telescope, allows for image manipulation beyond what a single lens can achieve, such as achieving high magnification while correcting for certain optical distortions.
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• Convex lens: converges light, forms real or virtual images. Concave lens: diverges light, always virtual, diminished image.
• Lens formula: 1/v - 1/u = 1/f.
• Lens power (P = 1/f in metres) is measured in dioptres; convex is positive, concave is negative.
• Combinations of lenses are used in cameras, microscopes, and telescopes.