Brief introduction on Light intensity quality, Invisible spectrum, EM radiation-properties, Theory of wave and quanta Radio-activity

1. Light intensity quality
Invisible spectrum
EM Radiation-properties
Theory of wave and quanta Radio-
activity
9/21/2021 1
GENERAL PHYSICS
Dr. Jonathan Lalrinmawia

2. Light intensity quality, Invisible
spectrum, EM radiation-properties
9/21/2021 2
GENERAL PHYSICS
What is light intensity and how is it
measured?
The amount of light (lumens) falling on a
surface (over any given square foot or
square meter).
It is measured in terms of lumens per
square foot (footcandles) or lumens per
square meter (lux). Or simply, It is
measured in footcandles or lux.

3. Light intensity quality, Invisible
spectrum, EM radiation-properties
9/21/2021 3
GENERAL PHYSICS
The SI unit of luminous intensity is the candela (cd)

4. Light intensity quality, Invisible
spectrum, EM radiation-properties
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GENERAL PHYSICS

5. Light intensity quality, Invisible
spectrum, EM radiation-properties
9/21/2021 5
GENERAL PHYSICS

6. Light intensity quality, Invisible
spectrum, EM radiation-properties
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GENERAL PHYSICS

7. Light intensity quality, Invisible
spectrum, EM radiation-properties
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GENERAL PHYSICS
What is EM radiation and its
characteristics?
EM radiation is an electric and
magnetic disturbance traveling
through space at the speed of
light.
It contains neither mass nor
charge but travels in packets of
radiant energy called photons,
or quanta.

8. Light intensity quality, Invisible
spectrum, EM radiation-properties
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GENERAL PHYSICS

9. Theory of wave and quanta
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GENERAL PHYSICS
Is light a particle or a wave!
Dual nature!

10. Theory of wave and quanta
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GENERAL PHYSICS
The dual nature of light as "both a particle and a
wave" has been proved, its essential theory was
further evolved from electromagnetics into
quantum mechanics. Einstein believed light is a
particle (photon) and the flow of photons is a
wave.

11. 7. Radioactivity
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GENERAL PHYSICS
Radioactivity: the property possessed by
some elements of spontaneously emitting
energetic particles by the disintegration of
their atomic
Nuclei.

12. Radioactivity
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GENERAL PHYSICS
Radioactive Decay
There are three types of radioactive decays
in nature:
α-decay –a helium nucleus (4
2He) is
emitted
β-decay – where electrons or positrons
are emitted;
γ-decay – high energy photons are
emitted.

13. Radioactivity
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GENERAL PHYSICS
Radioactive substances are atoms that
decay naturally. They can give off
alpha particles, beta
particles and gamma radiation.
Common Radioactive substances are:
Unranium, Radium, Cesium