20 Physics -- Lenses

Define the following terms : Centre of curvature, Radius of Curvature, Principal Axis, Optical Centre , Principal Focus , Focal length & Focal plane .

Define the following terms : Centre of curvature, Radius of Curvature, Principal Axis, Optical Centre , Principal Focus , Focal length & Focal plane .

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1. Centre of curvature: The centre of curvature is the center of the sphere from which a curved mirror or lens is derived. For a concave mirror or a convex lens, it is the center of the sphere of which the reflecting surface or the refracting surface is a part.

2. Radius of curvature: The radius of curvature is the distance between the centre of curvature and the vertex (the geometric center) of a curved mirror or lens. It is denoted by the symbol 'R'.

3. Principal axis: The principal axis is an imaginary line passing through the centre of curvature and the vertex of a curved mirror or lens. It is the axis around which the mirror or lens is symmetrical.

4. Optical centre: The optical centre is the geometric center of a lens. It is the point on the principal axis through which light passes undeviated. For thin lenses, the optical centre coincides with the lens's physical center.

5. Principal focus: The principal focus is a point on the principal axis of a curved mirror or lens where parallel rays of light converge or appear to diverge from. For a concave mirror or a convex lens, the principal focus is in front of the mirror or lens if it converges light, or behind the mirror or lens if it diverges light.

6. Focal length: The focal length is the distance between the principal focus and the vertex of a curved mirror or lens. It is denoted by the symbol 'f'. It determines the amount of bending or focusing power of the mirror or lens. A shorter focal length implies stronger bending or focusing.

7. Focal plane: The focal plane is the plane perpendicular to the principal axis that passes through the principal focus. It is the plane where the focused image or light rays converge or appear to diverge.

Why can we see virtual images? It cannot be formed on the screen. The retina in our eye acts as a screen. If the image cannot be formed on the screen, why can we see it?

It is better to have brief account to working mechanism of eye before reaching out this question.

Whenever the rays of light coming from virtual object i.e. divergent rays of light fall in our eye lens which is a convex lens, it converges the rays of light forming the real image in our retina making us able to see the objects.

Derive lense formula for convex lense

A water droplet in a leaf has radius of Curvature R and refractive index of 1.33 . Can it form an image of the Sun on the leaf ?

No,it cannot form the image.

Explanation:-

A certain eyeglass lens is thin at its centre, even thinner at its top and bottom edges, and relatively thick at its left and right edges. What defects of vision is this lens intended to correct?I)...

in which condition does a convex lens from and enlarged image. give the application of this condition

If a converging lens and a diverging lens having the same focal length be in contact, how will the combination of lenses behave?

Does the focal length of a lens change when immersed in water ? Will it increase or decrease?

When a lens is immersed in water, its focal length will generally decrease due to the change in refractive medium. If water has a higher refractive index than the lens material, the lens behaves as if it is in a more optically dense medium, resulting in a shorter focal length.

Define power of lens ? Write it's SI unit ?

Power of lens is a measure of its ability to produce deviation of light. The SI unit of power of lens is Dioptre 'D'

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