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this is light

1. LIGHT
CLASS 10
TH
BY- DHRUV KOLI

2. REFELCTION
OF LIGHT
Laws of reflection-
1.The angle of incidence is equal to the angle of reflection, and
2. The incident ray, the normal to the mirror at the point of
incidence and the reflected ray, all lie in the same plane
Properties of image formed by Plane mirror-
1.Virtual and erect image
2.Same size as that of object
3.Laterally inverted (left side of the object is seen as the right
side of the image)
4.Image is as far behind as the object is from the mirror
Curved mirror: Mirror which are made up of curved surfaces
Spherical mirror: Mirrors which are a part of a spherical surface.
Spherical mirrors are a type of curved mirrors

3. SPHERICAL
MIRRORS
•Concave mirror: spherical mirror whose reflecting surface is curved inward
•Convex mirror: spherical mirror whose reflecting surface is curved outwards
•Important term-
1.Pole (P) – The center of reflecting surface
2.Centre of curvature (C)- the centre of the sphere of which the spherical mirror
is a part.
3.Radius of curvature (R)- the radius of the sphere of which the spherical mirror
is a part
4.Principal axis- straight line passing through the centre of curvature and the
pole
5.Focus (F)- point where the parallel light rays converge after passing being
reflected by the spherical mirror
6.Focal length (f)- the distance between the focus and the pole
7.Aperture- the diameter of the reflecting surface
R=2f

4. SPHERICAL MIRRORS
Aperture

5. IMAGE
FORMATION
BY
SPHERICAL
MIRROR

6. USES OF
CONVEX
MIRRORS
•Convex mirrors are commonly used as rear-view (wing)
mirrors in vehicles.
•Convex mirrors are preferred because they always give an
erect, though diminished, image.
Also, they have a wider field of view

7. SIGN
CONVENTION
FOR
SPHERICAL
MIRRORS

8. MIRROR
FORMULA
Mirror formula-
1
�
+
1
�
=
1
�
Magnification:
It is expressed as the ratio of the height of the image to the
height of the object.
m=
ℎ
′
ℎ
=−
�
�
A negative sign in the value of the magnification indicates
that the image is real
A positive sign in the value of the magnification indicates
that the image is virtual.

9. REFRACTION
OF LIGHT
the bottom of a tank or a pond containing water appears to
be raised. Why?
when a thick glass slab is placed over some printed matter,
the letters appear raised when viewed through the glass
slab. Why does it happen?
the apparent displacement of a pencil, partly immersed in
water. But why?
It appears that when travelling obliquely from one medium
to another, the direction of propagation of light in the second
medium changes. This phenomenon is known as refraction
of light.

10. REFRACTION
THROUGH A
RECTANGULAR
GLASS SLAB
1. The incident ray, the refracted ray and the normal to the interface
of two transparent media at the point of incidence, all lie in the
same plane.
2. The ratio of sine of angle of incidence to the sine of angle of
refraction is a constant, for the light of a given colour and for the
given pair of media. This law is also known as Snell’s law of
refraction. (This is true for angle 0 < i < 90)
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11. THE
REFRACTIVE
INDEX
The refractive index of medium 2 with respect to medium 1 is
given by the ratio of the speed of light in medium 1 and the
speed of light in medium 2. This is usually represented by the
symbol n21 .
&#3627408475;
21=
&#3627408480;&#3627408477;&#3627408466;&#3627408466;&#3627408465; &#3627408476;&#3627408467; &#3627408473;??????&#3627408468;ℎ&#3627408481; ??????&#3627408475; &#3627408474;&#3627408466;&#3627408465;??????&#3627408482;&#3627408474; 1
&#3627408480;&#3627408477;&#3627408466;&#3627408466;&#3627408465; &#3627408476;&#3627408467; &#3627408473;??????&#3627408468;ℎ&#3627408481; ??????&#3627408475; &#3627408474;&#3627408466;&#3627408465;??????&#3627408482;&#3627408474; 2
=
&#3627408483;1
&#3627408483;2
&#3627408475;
12=
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&#3627408480;&#3627408477;&#3627408466;&#3627408466;&#3627408465; &#3627408476;&#3627408467; &#3627408473;??????&#3627408468;ℎ&#3627408481; ??????&#3627408475; &#3627408474;&#3627408466;&#3627408465;??????&#3627408482;&#3627408474; 1
=
&#3627408483;2
&#3627408483;1
The absolute refractive index of a medium is simply called
its refractive index.
&#3627408475;
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&#3627408480;&#3627408477;&#3627408466;&#3627408466;&#3627408465; &#3627408476;&#3627408467; &#3627408473;??????&#3627408468;ℎ&#3627408481; ??????&#3627408475; ????????????&#3627408479;
&#3627408480;&#3627408477;&#3627408466;&#3627408466;&#3627408465; &#3627408476;&#3627408467; &#3627408473;??????&#3627408468;ℎ&#3627408481; ??????&#3627408475; &#3627408474;&#3627408466;&#3627408465;??????&#3627408482;&#3627408474;
=
&#3627408464;
&#3627408483;

12. REFRACTION BY
SPHERICAL LENSES
•A transparent material bound by two surfaces,
of which one or both surfaces are spherical,
forms a lens.
•A lens may have two spherical surfaces,
bulging outwards. Such a lens is called a
double convex lens. It is simply called a convex
lens. It is thicker at the middle as compared to
the edges. Convex lens converges light rays
•A double concave lens is bounded by two
spherical surfaces, curved inwards. It is thicker
at the edges than at the middle. Such lenses
diverge light rays

13. IMAGE
FORMATION BY
LENSES

14. LENS FORMULA
AND
MAGNIFICATION
Lens formula-
1
&#3627408483;
−
1
&#3627408482;
=
1
&#3627408467;
Magnification:
It is expressed as the ratio of the height of the image to the
height of the object.
m=
ℎ
′
ℎ
=−
&#3627408483;
&#3627408482;
A negative sign in the value of the magnification indicates
that the image is real
A positive sign in the value of the magnification indicates
that the image is virtual.

15. POWER OF A
LENS
The degree of convergence or divergence of light rays
achieved by a lens is expressed in terms of its power. The
power of a lens is defined as the reciprocal of its focal length
The SI unit of power of a lens is ‘dioptre’.
1 dioptre is the power of a lens whose focal length is 1 metre.