Light is a form of energy that allows us to see objects when it reflects off of them and into our eyes. Light travels in straight lines. Reflection can be regular (from smooth surfaces) or diffuse (from rough surfaces). The laws of reflection state that the angle of incidence equals the angle of reflection and that the incident, reflected, and normal rays all lie in the same plane. Real images are formed when light rays converge at a point, while virtual images appear to be located where the light rays diverge. Kaleidoscopes and periscopes use multiple reflections to produce symmetrical patterns or allow viewing around obstacles. Dispersion is the separation of light into its component wavelengths, causing the spectrum. The human eye

2. Definition
• (i) Light is a form of energy which helps us to
see objects.
• (ii) When light falls on objects, it reflects the
light and when the reflected light reaches
our eyes then we see the objects.
• (iii) Light travels in straight line.
• (iv) The common phenomena of light are
formation of shadows, formation of images
by mirrors and lenses, bending of light by a
medium, twinkling of stars, formation of
rainbow etc.

4. Company
LOGO Reflection
 Reflection of light is either specular
(mirror-like) or diffuse (retaining the
energy, but losing the image) depending
on the nature of the interface.
Furthermore, if the interface is between a
dielectric and a conductor, the phase of
the reflected wave is retained, otherwise if
the interface is between two dielectrics,
the phase may be retained or inverted,
depending on the indices of refraction.

6. Laws Of Reflection
(i) The angle of incidence is equal to the
angle of reflection.
(ii) The incident ray, the reflected ray and the
normal to the mirror at the point of incidence
all lie in the same plane.

7. Regular And Diffused Reflection
• Regular Reflection – A smooth surface
gives a sharp and clear image. Reflection
of light from a smooth mirror is called
regular reflection.
• Diffused Reflection – The reflected light
falls over a larger area and the image
formed is not sharp and clear. This type of
reflection is called irregular or diffused
reflection.

9. Real And Virtual Image
• Real Image – a real image is an image in which the
outgoing rays from a point on the object pass through a
single point. It is easiest to observe real images when
projected on an opaque screen (although a screen is not
necessary for the image to form).
• Virtual Image – A virtual image is an image in
which the outgoing rays from a point on the object
always diverge. It will appear to converge in or behind
the optical device (e.g., a mirror). A simple example is a
flat mirror where the image of oneself is perceived at
twice the distance from oneself to the mirror.

11. Kaleidoscope
• A Kaleidoscope operates on the principle
of multiple reflection, where several
mirrors are together. Typically there are
three rectangular lengthwise mirrors.
Setting the mirrors at a 60-degree so that
it forms a triangle. 60 degree angle apart
from each other creates eight duplicate
images of the objects, six at 60°, and 2 at
90°. As the tube is rotated, the tumbling of
the coloured objects presents varying
colours and patterns.

13. Periscope
• A periscope is an instrument for
observation from a concealed position. In
its simplest form it consists of an outer
case with mirrors at each end set parallel
to each other at a 45-degree angle. This
form of periscope, with the addition of two
simple lenses, served for observation
purposes in the trenches during World
War I.

14. • Principle of the periscope. The periscope on the left uses
mirrors whereas the right uses prisms.
a Mirrors
b Prisms
c Observer's eye

15. Dispersion Of LightDispersion Of Light
• Dispersion is the phenomenon in which the
phase velocity of a wave depends on its
frequency, or alternatively when the group
velocity depends on the frequency. Media having
such a property are termed dispersive media.
Dispersion is sometimes called chromatic
dispersion to emphasize its wavelength-
dependent nature, or group-velocity
dispersion (GVD) to emphasize the role of the
group velocity.

16. Dispersion of sunlight by a prism

17. The Human Eye
 The human eye is an organ which
reacts to light for several purposes.
As a conscious sense organ, the
mammalian eye allows vision. Rod
and cone cells in the retina allow
conscious light perception and
vision including color differentiation
and the perception of depth. The
human eye can distinguish about 10
million colors.

19. Defects Of Vision
Myopia - Nearsightedness, also called myopia
is common name for impaired vision in which a
person sees near objects clearly while distant
objects appear blurred. In such a defective eye,
the image of a distant object is formed in front of
the retina and not at the retina itself.
Hypermetropia - Farsightedness, also called
hypermetropia, common name for a defect in
vision in which a person sees near objects with
blurred vision, while distant objects appear in
sharp focus. In this case, the image is formed
behind the retina.

21. The Braille System
• Braille is a tactile writing system used by
the blind and the visually impaired, and
found in books, on menus, signs, elevator
buttons, and currency. Braille-users can
read computer screens and other
electronic supports thanks to refreshable
Braille displays. They can write Braille with
a slate and stylus or type it on a Braille
writer, such as a portable Braille note-
taker, or on a computer that prints with a
Braille embosser.

23. Submitted By:-
• Name – Karan Singh
Rawat
• Class – VIII
• Section – C
• Roll No. - 10