# JEE Main & Advanced Physics Ray Optics Rules of Image Formation by Lens

Rules of Image Formation by Lens

Category : JEE Main & Advanced

Convex lens : The image formed by convex lens depends on the position of object.

(1) When object is placed at infinite (i.e. $u=\infty$)

Image

$\to$         At F

$\to$         Real

$\to$         Inverted

$\to$         Very small in size

Magnification $m<<-1$

(2) When object is placed between infinite and 2F (i.e. $u>2f$)

Image

$\to$         Between F and 2F

$\to$         Real

$\to$         Inverted

$\to$         Very small in size

Magnification $m<-1$

(3) When object is placed at 2F (i.e. $u=2f$)

Image

$\to$         At 2F

$\to$         Real

$\to$         Inverted

$\to$         Equal in size

Magnification $m=-1$

(4) When object is placed between F and 2F (i.e. $f<u<2f$)

Image

$\to$         Beyond 2F

$\to$         Real

$\to$         Inverted

$\to$         Large in size

$\to$         Magnification $m>-1$

(5) When object is placed at F (i.e. $u=f$ )

Image

$\to$         At $\infty \ ] \[\to$         Real

$\to$         Inverted

$\to$         Very large in size

Magnification $m>>-1$

(6) When object is placed between F and optical center (i.e. $u<f$)

Image

$\to$         Same side as that of object

$\to$         Virtual

$\to$         Erect          large in size

Magnification $m>1$

Concave lens : The image formed by a concave lens is always virtual, erect and diminished (like a convex mirror)

(1) When object is placed at $\infty$

Image

$\to$         At F

$\to$         Virtual

$\to$         Erect

$\to$         Point size

Magnification $m<<+1$

(2) When object is placed any where on the principal axis

Image

$\to$         Between optical centre and focus

$\to$         Virtual

$\to$         Erect

$\to$         Smaller in size

Magnification $m<+1$

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