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1. CHHAYA Y KADAM
B.Ed Second Semester
Topic; Light
K.L.E Society’s Of Education
Vidyanagar Hubballi

2. Light or visible light is electromagnetic radiation within the portion of
the electromagnetic spectrum that is perceived by the human eye.[1] Visible
light is usually defined as having wavelengths in the range of 400–
700 nanometres (nm), corresponding to frequencies of 750–420 terahertz,
between the infrared (with longer wavelengths) and the ultraviolet (with
shorter wavelengths).[2][3]
In physics, the term "light" may refer more broadly to electromagnetic
radiation of any wavelength, whether visible or not.[4][5] In this sense, gamma
rays, X-rays, microwaves and radio waves are also light. The primary
properties of light are intensity, propagation direction, frequency or
wavelength spectrum and polarization.

3. Laws of reflection
Definition:
The law of reflection defines that upon reflection
from a smooth surface, the angle of the reflected ray is
equal to the angle of the incident ray, with respect to
the normal to the surface that is to a line perpendicular
to the surface at the point of contact.
The reflected ray is always in the plane defined by
the incident ray and the normal to the surface at the
point of contact of the incident ray.
The images produced by plane mirrors and curved
mirrors can be understood by the law of reflection.

4. The process through which light rays fall on the surface and get
bounced back is known as a reflection of light.
Types of Reflection
Regular Reflection:
The plane mirrors with a smooth surface produce this type of
reflection. In this case, the image is clear and very much visible.
The images produced by plane mirrors are always virtual, that is
they cannot be collected on a screen.
In the case of curved mirrors with a smooth surface, we can see the
images of reflection either virtually or really. That is, the images
produced by curved mirrors can be either real (collected on a screen
and seen), or virtual (cannot be collected on a screen, but only seen).

5. Irregular Reflection:
Unlike mirrors, most natural surfaces are rough on the scale of the
wavelength of light, and, as a consequence, parallel incident light rays are
reflected in many different directions irregularly, or diffusely. Hence,
diffuse reflection helps in seeing the objects and is responsible for the
ability to see most illuminated surfaces from any position.

6. The law of reflection formula is given as:
θi = θr
Where,
θi is the angle of incidence
θr is the angle of reflection

7. Concave Mirrors:
By reflection of light, concave mirrors give real,
inverted images if the object is beyond the focus and a
virtual, erect, enlarged image if the object has a distance
less than the focal length from the pole of the mirror.

8.  Concave mirrors are used in torches, searchlights, and
headlights of vehicles to get powerful parallel beams of
light.
 Concave mirrors are also used as shaving mirrors to see
a larger image of the face.
 Dentists use concave mirrors to see bigger images of
the teeth of the patients.
 Large concave mirrors are used to focus sunlight to
produce heat in the solar furnaces.

9. Convex Mirrors:
By the reflection of light convex Mirrors always
give a virtual, erect, diminished image of the object
kept infront of the mirror.

10. Uses of Convex Mirrors:
•The convex mirror is used as a side-view mirror in vehicles to
give a smaller view of the vehicles coming from behind.
•They are used in shops and supermarkets and any other place
where there is a requirement for detecting burglars.
•Convex mirrors are used in making lenses for sunglasses.
•Convex mirrors are used in magnifying glasses, and
telescopes.
•Convex mirrors are used to reflect street light; because they
can reflect over a wide area.
•Convex mirrors are kept at the street corners to avoid
collisions.

11. When light passes from a denser medium to
a lighter medium at an angle more than the critical
angle required for refraction, then the light is
reflected back into the denser medium. This is a
phenomenon called Total Internal Reflection. The
light undergoing the total internal reflection also
follows the ordinary laws of reflection for light as
shown below:

12. Total Internal Reflection

13. The phenomenon, total internal reflection, is taken
advantage of fibre in piping light in a curved path. The
light directed down a narrow fibre of glass or plastic
repeatedly reflects from the fibre-air interface at an angle
larger than the critical angle. Optical fibres can transmit
light over long distances without any loss of intensity.
Sequences of light pulses are used to transmit
information through an optical fibre network with the
help of this total internal reflection. Medical instruments
like ‘endoscopes’ use the total internal reflection of light
through an optical fibre bundle to image internal organs.

14. •Reflection is used in periscopes to view advancing enemies
on the battlefield from a safe position.
•Reflection is the reason why we see objects.
•Reflection by a concave mirror and a convex mirror has
many uses as listed above.
•Reflection helps in medical diagnosis and optical
communications.
•Light and Sound both follow the law of reflection, both
being waves.
•Using the law of reflection for sound and light, we can
measure the distances accurately to objects.
•Reflection is the reason why we hear the echo of sound.