Question

What would your image look like if you stood close to a large:
A) Convex mirror?
B) Concave mirror?
Give reasons for your answer.

Answer 1

Lens formula which gives a relationship between object distance, image distance and focal length. If the focal length is positive then the system will converge rays of light and if it is negative then the system will diverge rays of light.
Lens formula is given by:
$\dfrac{1}{v}=\dfrac{1}{u}=\dfrac{1}{F}$
Where $u$ =object distance
$v$ =image distance
$F$ =focal length

Complete step-by-step answer:
The position and the size of the image are obtained by using lens formula and also by using magnification formula. The focal length is a measure of how strongly the system can converge or diverge rays of light and the focal length of concave lens and convex lens are different. The focal length is half of the radius of curvature in the case of a mirror.
Convex mirror is a curved mirror for which the reflective surface bulges out towards the light source. Convex mirrors reflect light outwards and therefore they are not used to focus light. The image is virtual, erect and smaller in size than the object, but gets larger as the object comes towards the mirror. Such mirrors are also called diverging mirrors.
If we stand close to a large convex mirror then our image will be diminished and erect because when the object lies anywhere between the pole and infinity, the concave mirror forms a diminished, virtual and erect image.
If we stand close to a large concave mirror then our image will be enlarged, virtual and erect because when an object lies within the focus of a concave mirror, it forms an enlarged, virtual and erect image.

Note: Students the polarity of focal length is negative for concave lens and it is positive for convex lens. Concave lens always forms a virtual and erect image while the convex lens forms a real and inverted image. By using lens maker formula we can build a lens with required focal length and there is standard value for focal length.