Light Reflection and refraction

1. Darshil Kumar
Reflection of
Light

2. Reflection of Light with basics.
Reflection through Spherical Mirrors.
Sign Convention & Formulae.
WHAT WE'LL DISCUSS...

3. REFLECTION OF
LIGHT
It should have
shiny surface.
It should have
smooth surface.
It is the bouncing back of light
rays on striking the surface.
It should have
polished surface .
Characteristics of Best Reflector

4. SPHERICAL
PLANE
CONVEX CONCAVE
Incident ray, reflected ray &
normal lie on the same plane.
Is that in which
reflection occurs through
outer surface of mirror.
Is that in which reflection
occurs through inner
surface of mirror.
TYPES OF MIRROR
Laws of Reflection
Angle of incidence is always
equal to the angle of
reflection.

5. VIRTUAL
REAL
Is that in which image
is formed when
reflected rays actually
meet at a certain point.
Is that in which image is
formed when reflected
rays do not meet actually
but appear to meet at
certain point.
TYPES OF IMAGE
It is always inverted.
It can be obtained on screen It is always erect.
It can't be obtained on screen.

6. IMAGE FORMATION BY
PLANE MIRROR

7. But, what is the
nature of the
image formed?
The image formed is virtual & erect.
The image is of the same size as
object.
The image is at the same distance
behind the mirror as the object is
in front of the mirror.
The image is laterally inverted i.e.
sideways reversed

8. REFLECTION
THROUGH SPHERICAL
MIRRORS
As we have discussed
earlier, there are two
types of spherical mirror
i.e. Concave & Convex.

9. 1. Concave mirror
Converging mirror

10. 2. Convex mirror
Diverging mirror

11. Terms
Apperture-
Centre of Curvature (C)-
Radius of Curvature (R)-
Principal focus (F)-
Pole (P)-
The diameter of the reflecting surface of
spherical mirror is called its aperture.
It is the point between centre of Curvature and
Pole where all reflected rays of parallel incident
rays actually meet or appear to meet.
It is the point where principal axis strikes the mirror.
It is the centre of the spherical mirror.
It is the distance between centre of Curvature
and Pole.

12. Rules to obtain image from
Concave mirror.
1.
2.
A ray of light which is parallel to the P. axis of
of a concave mirror, passes through its focus
after reflection from the mirror.
A ray of light passing through the centre of
Curvature of a concave mirror is reflected back
along the same path.

13. 3.
A ray of light passing through the focus of a
concave mirror becomes parallel to the
principal axis after reflection.
A ray of light which is incident at the pole of a
concave mirror is reflected back making the
same angle with the principal axis.

14. Rules to obtain image from
Convex mirror.
1.
2.
The incident ray which is parallel to the P.axis
of a convex mirror diverge but appears to be
coming from its focus after reflection from the
mirror.
A ray which is directed towards the principal
focus of a convex mirror, after reflection, will
emerge parallel to the P.axis.

15. 3.
A ray of light which is incident at the pole of a
convex mirror is reflected back making the
same angle with P.axis.
A ray of light going towards the 'C' of a convex
mirror is reflected back along the same path.

16. Image formations by a
Concave mirror .
1. 2.
When the object is at infinity: When the object is placed beyond C:
Characteristics:
Image formed at the focus.
Image is real & inverted.
Image is much smaller than the object.
Characteristics:
Image formed between 'f' & 'C'.
Image is real and inverted.
Image is smaller than the object.

17. 3. When the object is at 'C': When the object is between'F' & 'C':
Characteristics:
Image formed at the 'C'.
Image is real & inverted.
Image is of the same size.
Characteristics:
Image is formed beyond the 'C'.
Image is real and inverted.
Image is larger than the object.

18. When the object is at 'F': When the object is between'P' & 'F':
Characteristics: Characteristics:
Image is formed at infinity.
Image is real & inverted.
Image is highly magnified
Image formed is behind the mirror.
Image is virtual & erect.
Image is larger than the object.

19. Image formations by a
Convex mirror .
1. 2.
When the object is at infinity:
When the object is placed b/w pole &
infinity:
Characteristics: Characteristics:
Image formed behind the mirror at 'F'.
Image is virtual & erect.
Image is highly diminished.
Image is behind the mirror b/w 'P' & 'F'.
Image is virtual & erect.
Image is smaller than the object.

20. USES OF CONCAVE
MIRROR:
It is used in Torches-
It is used in making Solar devices-
It is used as shaving mirrors-
It is used by dentist to see cavities-
As it produces powerful beam of light rays
that converge at infinity.
As it converges all the rays so when solar rays converge,
they increase the temperature at that converging point.
As when face is placed b/w pole & focus it gives virtual,
erect & magnified image.
As when tooth is placed b/w pole & focus it gives
virtual, erect & magnified image.

21. Is there any use
of Convex
mirror?
It is used as a rear view mirror as it
gives virtual & diminished image, it
covers wide view, Image formed is
within focus.

22. Sign Convention &
Formulae
+x
-X
+y
-y

23. Sign Convention is also known as New Cartesian Sign Convention. In this
convention, the pole (P) of the mirror is taken as the origin. The principal axis
of the mirror is taken as the x-axis (X',X) of the coordinate system. The
conventions are as follows:
The object is always placed to the left of the corner. This implies
that the light from the object falls on the mirror from the left hand
side .
Distances measured perpendicular to & above the P.axis
(along+y-axis) are taken as positive.
Distances measured perpendicular to & below the P.axis
(along-y-axis) are taken as negative.
All distances parallel to the P.axis are measured from
the pole of the mirror.
All the distances measured to the right of the origin (along + x-
axis) are taken as positive while those measured to the left of the
origin (along -x-axis) are taken as negative.

24. Object distance
is always negative
in the spherical
mirrors.
IT'S A WRAP!
From the two previous slides I
have drawn a conclusion:
ALSO:
Height of object is always
positive in the spherical mirrors.

25. FORMULAE
Here,
v— Image distance
u— Object distance
f— focal length
1) Mirror Formula

26. 2) Magnification
m=
hi
ho
m=
Magnification produced by a spherical
mirror gives the relative extent to which
the image of an object is magnified with
respect to the object size.
-v
u
Here,
m— Magnification
hi— Image distance
ho— Object distance
v— Image distance
u— Object distance

27. Tools for Magnification:
B
If the Magnification is positive than the
image is virtual & erect.
If the Magnification is negative
than the image is Real & inverted.

28. THANK YOU!
For giving your most precious time..