Biconvex Lens
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Biconvex Lens: Definition, Properties, Uses & FAQs
Biconvex Lens is a simple, symmetrical lens with two outward-curving (convex) spherical surfaces, typically having equal radii of curvature. Biconvex lenses are widely used in optical instruments, magnifiers, and imaging systems due to their powerful converging properties.
What is a Biconvex Lens?
- A biconvex lens (also called a convex-convex lens) has two convex (outwardly curved) surfaces.
- It converges parallel light rays to a focal point behind the lens, making it a positive lens.
- The human eye’s lens is a natural example of a biconvex lens.
Properties of Biconvex Lenses
- Possess positive focal length (shorter for more curved lenses).
- Can converge incident light to a focus (real or virtual images).
- Symmetrical shape, with equal radii of curvature on both surfaces.
- Capable of minimizing spherical aberration and distortion at certain conjugate ratios.
- Can form both real and virtual images, depending on object placement.
Uses & Applications of Biconvex Lenses
- Used as magnifying glasses and burning glasses.
- Essential component in microscopes, telescopes, cameras, projectors, and binoculars.
- Used to focus laser beams and in optical relays.
- Present in the human eye for focusing light onto the retina.
- Used in various laboratory and industrial optical devices.
Practice MCQs: Biconvex Lens
- A biconvex lens has: a) Two concave surfaces
b) One convex, one concave surface
c) Two convex surfaces
d) Flat surfaces only - Which property is true for a biconvex lens? a) It diverges all parallel rays
b) It converges parallel rays
c) Has negative focal length
d) None of these - Which of these devices uses a biconvex lens? a) Bar magnet
b) Ammeter
c) Microscope
d) Resistor - The focal length of a biconvex lens is: a) Always negative
b) Always positive
c) Zero
d) Infinite
Answers: 1-c, 2-b, 3-c, 4-b
Frequently Asked Questions (FAQs) about Biconvex Lenses
- What is a biconvex lens?
A biconvex lens is a simple lens with two outward-curved (convex) spherical surfaces, commonly used to converge light and form real or virtual images. - Why is a biconvex lens called a converging lens?
Because it brings parallel rays of light to a single focus, forming a real image behind the lens. - Where is the biconvex lens used in daily life?
It is used in eyeglasses, microscopes, cameras, telescopes, projectors, and as a magnifying glass. - What is the formula for the focal length of a biconvex lens?
1/f = (n-1) [1/R1 – 1/R2] where n is refractive index, R1 and R2 are radii of curvature. - Can a biconvex lens form both real and virtual images?
Yes, depending on the object's distance from the lens, it can form both real and virtual images. - What happens to parallel light rays after passing through a biconvex lens?
The rays converge at a point called the focal point, behind the lens. - Is the human eye lens biconvex?
Yes, the human eye lens is a natural biconvex lens, which adjusts its curvature to focus light on the retina. - What is the main difference between biconvex and plano-convex lens?
Biconvex lens has two convex surfaces, while plano-convex has one flat and one convex surface. - Do biconvex lenses have positive focal length?
Yes, all biconvex lenses have positive focal length. - Why are biconvex lenses preferred in optical instruments?
They minimize aberrations and provide symmetrical convergence of light, making them ideal for quality imaging and magnification.
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Last modified: Thursday, 24 July 2025, 10:34 AM