Question

define :

focal length
focus
optic centre
focal plane
principal axis

​

Answer 1

$\bold{Answer}$

$\bold{Focal \ Length :}$

Its a distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror to the point where parallel rays of light meet.

$\bold{focus :}$

Focus is also known as image point. This is a point where light ray originating from a point on the object converge, This called Focus.

$\bold{ Optical \ centre}$

A optical centre is a point on which the axis of a lens that is located that any ray of light passing through it in passing through the lens suffers no net deviation and that may be within, without, or on either surface of the lens.

$\bold{Focal \ plane}$

The focal plane is the plane that is perpendicular to the axis of a lens or mirror and passes through the focal point. 

$\bold{Principal \ axis}$

Principal axis is the line passing through the optical centre and centres of the curvature of the faces of a lens or a curved mirror, This called principal axis.

Answer 2

welcome to the optics

focal length :

Focal length: The focal length (denoted by FP in the fig.) is the distance between the pole P and the principal focus F of a curved mirror. The focal length is half the radius of curvature.

Focus

(Principal focus) It is a point on the principal axis of the mirror, such that the rays incident on the mirror parallel to the principal axis after reflection, actually meet at this point (in case of a concave mirror) or appear to come from it (in case of a convex mirror.

optic centre:

Optical centre(o):A point in or out of lens through which ray of light pass undeviated.

⏩The central point of a lens is its optical centre.

⏩It is usually represented by the letter O.

focal plane:

For objects a finite distance away, the image is formed at a different location, but rays that leave the object parallel to one another cross at the rear focal plane

principal axis :

the straight line passing through the centre of curvature and pole of a spherical mirror is called it's principal axis.

i hope it help you ❤️

follow me