Question

Define and show on a diagram, the following terms relating to a concave mirror:
(i) Pole (ii) Radius of curvature (iii) Focal length

Answer 1

(i) POLE $(P)$: The geometric centre of the concave mirror is known as the pole. It is taken supposed to be origin in the New Cartesian Sign Convention system.

(ii) RADIUS OF CURVATURE $(R)$: The radius of the sphere where the concave mirror is a part, is called the radius of curvature.

(iii) FOCAL LENGTH $(f)$: It is the distance between the focus and the pole of a concave mirror.

More:

• Relationship between Focal length and Radius of Curvature:-

$R = 2.f$

• Mirror formula:

$\dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u}$

• 'u', 'f' are always negative in case of concave mirror.
• Magnification formula:-

$m = \dfrac{h_e}{h_o} = - \dfrac{v}{u}$.

Magnification can be positive or negative.

• Negative magnification => real/inverted image.
• Positive magnification => virtual/erect.
• Aperture is the effective diameter of the reflecting surface of the mirror.

$I \propto \dfrac{\pi . d^2}{4}$

=> $(Intensity_{of Image}) \propto (Aperture)^2$