CHAPTER 7 : GEOMETRICAL OPTICS
MIRROR
CONVEX MIRROR (1 case)
*O-object, P-Parallel,
F-Focus
1. ray diagram (OPF, OFP, OCO)
1. ray diagram (OPF, OFP, OCO)
O
U = +ve, Front of
mirror (real object )
f = -ve, r = -ve, V = -ve,
All at the back of the
mirror (virtual)
h
1 1 1
  , m i ,
f v u
ho
REFRACTION
CONCAVE MIRROR (5 case)
m
Plane surface
U = +ve, f = +ve, r = +ve,
Front of mirror (real object )
I
V = -ve, Back of the
mirror (virtual
image )
v
v
or m   , m = positive, image is upright, m = negative, image is inverted
u
u
Spherical surface
Snell’s law
n1 n 2 n 2  n1
 
u v
r
Convex surface, +r
Concave surface, -r
Same side as object
( virtual image ), - v
Snell’s law n1 sin 1  n2 sin  2
Image opposite side of
object ( real image ),+v
CONVEX LENS
1. Ray diagram (OPF, OC, OFP)
LENS
CONCAVE LENS
1. Ray diagram (OPF, OC, OFP)
back
front
Focal length, +f
Converging lens
At back of lens (Real), +V
Focal length, -f
Diverging lens,
Virtual image, -V
onvex surface, +r,
h
1 1 1
  , m i ,
f v u
ho
m
Concave surface, -r
 1 1 
1  n2
v
v
or m   , m = +, image is upright, m = -ve, image is inverted,
   1  
u
u
f  n1
 r1 r2 
2. COMBINATION OF 2 LENS
Final magnification, m f  m1 m 2
Law of Reflection
1. The incident ray, the reflected ray & the normal all lie in the same plane.
2. Angle of reflection, r equals the angle of incidence, i
Law of Refraction
1. The incident ray, refracted rays & the normal lie in the same plane. 2. n1 sin  1  n 2 sin  2