Chapter 10: Light- Reflection and Refraction
1.
When
light falls on a body, it may be absorbed, may be transmitted or light may come
back to the same medium.
2. Reflection of a light means light
waves are neither transmitted nor absorbed but are deflected from the surface
of the medium back into the same medium.
3.
Laws
of Reflection :
First law of reflection:
The incident ray, the normal to the surface at the point of incidence and the
reflected ray, all lie in the same plane.
Second law of reflection:
The angle of incidence is equal to the angle of reflection.
4. Real image is obtained when the rays
of light after reflection, actually converge at a point. It can be obtained on
the screen and can be seen with the eye.
5.
Virtual
image forms when rays of light do not actually meet, but appear to meet when
produced backwards. It cannot be obtained on the screen.
6.
Characteristics
of the image formed by the plane mirror :
i.
The
image formed by a plane mirror is always virtual and erect.
ii.
Size
of image = Size of object and the image is laterally inverted.
iii.
The
image formed by the plane mirror is as far behind the mirror as the object is
in front.
7. Lateral Inversion: The phenomenon due
to which the right side of the object appears as left and the left side of the
object appears as right. That is the image is inverted sideways.
8. A spherical mirror whose reflecting
surface is curved outwards and polished on the inner spherical surface is
convex mirror.
9.
A
spherical mirror whose reflecting surface is curved inwards and polished on the
outer spherical surface is concave mirror.
10.
Concave mirror
mostly forms real images, which can be received on the screen.
11.
Convex mirror
forms virtual images, which cannot be received on the screen.
12.
Differentiating
between a plane mirror, a concave mirror and a convex mirror, without touching
them:
i)
If
the image formed is erect and is of same size as in reality then it is a plane
mirror.
ii)
If
the image formed is still erect but smaller in size then it is a convex mirror.
iii)
If
the image is erect but magnified when mirror is close to the object then it is
a concave mirror.
13. Solar concentrators use huge concave
mirrors to focus large amounts of solar energy thereby producing high
temperature conditions in a solar power plant.
14. Concave
mirrors are used as shaving and make up mirrors.
15. The centre of the reflecting surface
of a spherical mirror is a point called the pole of the mirror and usually
represented by P.
