The document provides information about light and its characteristics. It discusses that light is a form of electromagnetic radiation that can be perceived by the human eye. It travels in waves and its wavelength determines properties like color. The document then describes characteristics of light such as its speed changing between mediums while frequency remains the same. It also discusses terminology related to light like luminance, luminaires, and illuminance. The properties of light covered include reflection, refraction, dispersion, interference and polarization.

1. ARCHITECTURAL SERVICES
RAR - 406
TOPIC – INTRODUCTION OF LIGHT
SUBMITTED TO – AR. GOPAL SUBMITTED BY –
TOMAR POOJA SHARMA
PRATEEK SHARMA

2. LIGHT
Light or visible light is electromagnetic radiation within the
portion of the electromagnetic spectrum that can be
perceived by the human eye.
Light is a source of illumination, whether a natural one (like the
sun) or an artificial one (like your lamp).
Light is a form of energy that travels as waves. Their length —
or wavelength — determines many of light's properties.
When it comes to visible light, the highest frequency color,
which is violet, also has the most energy. The lowest frequency
of visible light, which is red, has the least energy.

3. CHARACTERISTICS OF LIGHT
• Light is an electromagnetic wave.
• Light travels in a straight line.
• Light is a transverse wave, and does not need any medium to travel. Light
can travel through vaccum.
• Its speed through vaccum is 3 × 108 m/s.
• The velocity of light changes when it travels from one medium to another.
• The wavelength (λ) of light changes when it goes from one medium to
another.
• The frequency (f) of the light wave remains the same in all media.
• Light gets reflected back from polished surfaces, such as mirrors, polished
metal surfaces, etc.
• Light undergoes refraction (bending) when it travels from one transparent
medium to another.
• Light does not need a material medium to travel, that is, it can travel
through a vacuum too.

4. TERMINOLOGY AND UNITS
LUMINANCE-
Amount of light emitted from an
object in a given direction. The
eye can see objects because
these send light to the eye.
Luminance indicates how much
luminous power will be detected
by an eye looking at the surface
from a particular angle of view.
Luminance is this an indicator of
how bright the surface will
appear.
It is measured in candelas per
sq.m (cd/m^2).

5. A LUMINAIRE-
It is a complete lighting unit ,
consisting of a lamp or lamps
together with the parts designed
to distribute or enhance the light,
position and protect the lamps,
and connect the lamps to power
supply.
ILLUMINANCE-
It is the ratio of the quantity of light
falling on a surface and the area
thatt is illuminated.
Illumination is the total luminous flux
incident on a surface per unit
area.
It is measure of how much incident
light illuminates the surface.SI unit -
lux or lumen /m^2

6. LUMINOUS FLUX (Lumens)-
The perceived total amount of
useful light from a source is the
sum of the Candela
measurements in all directions.
It is measured in Lumens (lm).
The figure is also independent of
distance from the lamp and says
nothing of the direction of the
light, the intensity of the source or
the brightness of an illuminated
surface, just the total visible light
in all directions.

7. WAVELENGTH-
Visible light is just a small part of the
spectrum of electromagnetic
radiation that includes radio waves
,heat , light, microwaves etc.
Each type of radiation covers a
range of wavelengths that are
measured in nanometers (one
millionth of a millimetre)
LUMINOUS INTENSITY-
Luminous intensity is a measurement
the light radiating from the lamp in
a particular direction disregarding
the intensity of light in other
directions.
It measured in Candela.

8. EFFICACY-
Luminous efficacy
is a measures of
how well a light
source produces
visible light .
EFFICIENCY-
light output from a
LUMINAIRE- as a
percent of light
output from the
bulb it uses.

9. NOMINAL POWER (Watts)
Most suppliers provide a
nominal power rating, rather
than the actual power
consumption of the lamp
under specific conditions.
The actual power
consumption at the lamp
input of most extra low
voltage DC lamps at normal
battery voltage is typically
ten to twenty percent below
the nominal.

10. PROPERTIES OF LIGHT
• Reflection of light
• Refraction of light
• Diffraction of light
• Transmission of light
• Propagation of light
• Interference of light
• Polarization of light
• Dispersion of light
• Scattering of light

11. REFLECTION OF LIGHT
• Light bounce off the surfaces like
mirrors such that that angle of
incidence is equal to the angle of
reflection.
• Reflection of light enables us to see.
• We see colors of different objects
due to reflection.
• We see non-luminous objects due
to the reflection of light.
• The number of things you see in a
day is due to the reflection of light.`

12. TYPES OF REFLECTION
● Regular reflection / Specular reflection
● Irregular reflection / Diffused reflection

13. REGULAR REFLECTION
• The nature of reflection
depends on the
smoothness of the
surface.
• For example, a smooth
surface of silver reflects
the ray of light in one
direction only.
• The reflection by these
smooth surfaces is
called regular reflection.
IRREGULAR REFLECTION
• Most of the objects in the
everyday world are not
smooth on the microscopic
level.
• The rough surfaces of
these objects reflect the
rays of light in many
directions. Such of
reflection is called irregular
reflection.

14. LAWS OF REFLECTION OF LIGHT
• The laws of reflection determine the
reflection of incident light rays on
reflecting surfaces, like mirrors,
smooth metal surfaces and clear
water. Let’s consider a plane mirror
as shown in the figure above. The
law of reflection states that
● The angle of incidence is equal to
the angle of reflection.
● The incident ray, normal ray,
reflected ray at the point of an
incident all lie on the same plane.`

15. REFRACTION OF LIGHT
● Refraction is the change in
the direction of a wave
passing from one medium to
another
● One of the best examples of this
is when a pencil is put in a half-
filled glass of water.
● Notice how the pencil above
the water looks normal, but
under the water, it looks bent
and slightly larger. This is
because of refraction.

16. CAUSES OF REFRACTION
A light ray refracts whenever it travels at an angle into
a medium of different refractive index.
This change in speed results in a change in direction.
As an example, consider air travelling into water.
The speed of light decreases as it continues to travel at
a different angle.
When light travels from air into glass, the light slows
down and changes direction slightly
When light travels from a less dense substance to a
denser substance, the refracted light bends more
towards the normal line.
If the light wave approaches the boundary in a
direction that is perpendicular to it, the light ray
doesn’t refract in spite of the change in speed.

17. Laws of Refraction of Light

18. TYPES OF REFRACTION
REFRACTION FROM RARER TO
DENSER MEDIUM - in such
cases, the relative refractive
index is greater than 1. The
angle of incidence is greater
than angle of refraction.
REFRACTION FROM DENSER TO
RARER MEDIUM -the relative
refractive index is less than 1 .
The angle of refraction is less
than the angle of incidence.

19. ABSORPTION OF LIGHT
Light absorption is a process by
which light is absorbed and
converted into energy.
The absorption of light is
therefore directly proportional
to the frequency.
If they are complementary,
light is absorbed.
If they are not complementary,
then the light passes through
the object or gets reflected.

20. CAUSE OF ABSORPTION OF LIGHT
At specific frequencies, the electrons of the atom
tend to vibrate.
When a light wave of the same natural frequency is
incident on the atom, the electrons of that atom will
be set into vibrational motion.
During vibration, electrons interact with neighbouring
atoms in such a manner it converts the vibrational
energy into thermal energy.
Hence, we can conclude that the selective
absorption of light occurs when the frequency of the
light matches the frequency at which the electrons in
the atoms vibrate.
Different atoms and molecules possess different
natural frequencies of vibration, hence they will
selectively absorb different frequencies of visible light.

21. DISPERSION OF LIGHT
The process in which light is
separated into it's color due to
the differences in degrees of
refraction.
The most familiar example of
dispersion is probably a
rainbow, in which dispersion
causes the spatial separation of
a white light into components of
different wavelengths (different
colors).

22. INTERFERENCE OF LIGHT
• Interference is a phenomenon in
which two waves superimpose to
form a resultant wave of greater of
lower amplitude. There is no loss of
energy during interference. It is
simply redistributed.
• Interference, in physics, the net
effect of the combination of two or
more wave trains moving on
intersecting or coincident paths.
• Example -is the soap bubble
illustrated is that reflects a variety of
beautiful colors when illuminated by
natural or artificial light sources.

23. POLARIZATION OF LIGHT
It is defined as a phenomenon caused
due to the wave nature of
electromagnetic radiation.
A light that is vibrating in one plane is
referred to as Polarized light.
And the process of transforming
unpolarized light into Polarized light is
known as Polarization of light
Example:- Three-dimensional movies are
produced and shown with the help of
polarization.
Polarization is used in sunglasses to
reduce the glare. It is used in seismology
to study earthquakes.

24. TRANSMISSION OF LIGHT
A simple definition of light transmission is: When light
travels through a medium such as glass without being
reflected absorbed or scattered. When this happens
light energy is not lost and can be considered 100%
transmitted.
When you shine light on an object, a number of things
can happen. Reflection is when light bounces off of a
surface. Specular reflection is when light reflects off of
a shiny surface like a mirror. Diffuse reflection, however,
is when light illuminates a dull object.

25. • When light moves
through a transparent
(or semi-transparent)
material, it can be
transmitted, absorbed,
or reflected.
• Transmission of light is
when light waves move
all the way through a
material without being
absorbed.

26. ELECTROMAGNETIC SPECTRUM
Electromagnetic radiation
can be expressed in terms of
energy, wavelength, or
frequency.Frequency is
measured in cycles per
second, or Hertz. Wavelength
is measured in meters. Energy
is measured in electron volts.
Each of these three quantities
for describing EM radiation
are related to each other in a
precise mathematical way.

27. VISIBLE SPECTRUM
Visible light is a
range of
wavelengths
in the
electromagne
tic spectrum
visible to the
human eye
(wavelengths
of about 390
to 700 nm).

28. THANKYOU