# Explain me sign convection for mirrors,lens,and spherical surfaces in simple way...

Shreyas Patil
131 Points
7 years ago
The sign convection always follows the graph sign.
Type of lens
u
v
f
Height of the image (hI
Height of the object (hO)

Real
Virtual
Real
Virtual
Real
Virtual

Convex
-
+
-
+
No virtual focus
-
+
+
Concave
-
No real image is formed
-
No real focus
-
No real image is formed
+
+

Hope this helps. Do approve my answer.
nath
122 Points
7 years ago
Hi ! Sunkari,
for all lenses , mirror and spherical mirror the distance on the principal axis are measure from the optical centre.
The distance measure in the direction of incident rays are (+ve) and the distance measure in the direction opposite to the incident rays is (-ve).
All distance measure above the principal axis are (+ve) and measure below the principal axis are (-ve).
type                     u               v                     f                         hi                                           ho
real         virtual     real      virtual      real        virtual
convex lens               –         +             –           +          NO         –            +                     +
Concave lens               –        No            –           No         –          No           +                     +

Convex mirror           -         No            +            +          +          +             No                  +
concave  ||                   –         –              +            –          –         +              –                     +

Umakant biswal
5349 Points
7 years ago
@ sunkari
1- all distance from principal axis are measured from optical enter .
2-the distance measure in the direction of incident ray are +ve and opp. to that are -ve
3- all distance above the principal axis are +ve , thus height of object of an erect image are +ve
4- below the principal axis its -ve
for convex
image – +ve ( real ) , -ve ( virtual )
object – +ve (real ) , virtual – no virtual focus
height –
real (-ve ) virtual ( +ve )
height of object – always +ve .