1. LIGHT & OTHER ELECTROMAGNETIC WAVES
CHAPTER 27
LIGHT & OTHER ELECTROMAGNETIC WAVES

2. Electromagnetic Waves:
Transverse waves produced by the motion of electrically charged particles.
The electric field and magnetic field waves at right angles to each other.

3. Electromagnetic Waves:
These waves vary depending on frequency and wavelength.
No medium required to travel.

4. Electromagnetic Waves:
Speed varies with the change in medium.
All electromagnetic waves travel at the same speed through a vacuum (3 x 108 m/s). Their wavelength and frequency are different.

5. Electromagnetic Waves:
They carry energy and have momentum.
They have both wave and particle like behavior.

10. RADIO WAVES MICROWAVES INFRARED VISIBLE LIGHT ULTRA VIOLET LIGHT
X-RAYS
GAMMA RAYS
FREQUENCY
INCREASES
WAVELENGTH
DECREASES
ENERGY
INCREASES

11. LIGHT
Light is composed of tiny “particles”.
These particle-like bundles of radiation are called photons.

12. Light produces interference patterns like water waves.
Higher the frequency of the electromagnetic waves, the greater the energy of the wave.
Light produces interference patterns like water waves.

13. RADIO WAVES
Have low frequency
and long wavelengths.
They have the lowest
photon energy.

14. RADIO WAVES
Radio waves are used to transmit radio and TV signals.
They are also used in cellular phones and cordless phones.

15. RADIO WAVES
The process of varying radio waves is called modulation.
Voice, light images, computer information, and music can be used
for modulation.

16. OTHER USES OF RADIO WAVES
Communications
Navigation and defense equipment
Weather Forecasting
4.TV signals
5. AM and FM radio signals
6. Airport air traffic controllers
7. Radar used by police cars

17. INFRA RED RADIATION
Has a wavelength slightly longer than visible light.
Your skin feels warm
outside because your
skin is absorbing
infrared radiation
from the sun.

18. A thermogram is produced by measuring the infrared radiation given off by different parts of the body.
Tumors are detected by thermograms because they are warmer than other parts of the body.

19. Some security systems are designed to detect objects giving off infra red radiation and to respond by activating an alarm.

20. Infrared radiation are used to warm and dry objects.
Infra red lamps in
some restaurants
keep the food
warm until served.

21. Infrared images obtained from
Infrared images obtained from sensors on airplanes can yield important information on the health of crops and help us see
forest fires even
enveloped in an
opaque layer of
smoke.

22. Increasing Wavelength
Decreasing Frequency

23. VISIBLE LIGHT

24. VISIBLE LIGHT
It is the only part of the electromagnetic spectrum that we can see.
Violet Color has a smaller wavelength than red color.

25. ULTRA VIOLET RADIATION
They have higher frequency than visible light.
Exposure to UV radiation enables skin cell to manufacture vitamin D, which is needed for healthy bones and teeth.

26. ULTRA VIOLET RADIATION
Ultra violet lamps are used in hospitals to kill bacteria and viruses, and to sterilize surgical instruments.

27. ULTRA VIOLET RADIATION
UV rays are used to kill microorganisms in food and on hospital equipment.
Some minerals like fluorite and scheelite become fluorescent when exposed to UV light. Fluorescence occurs when a material absorbs UV radiation and re-emits visible light.

28. EXCESS OF ULTRA VIOLET RADIATION
Lead to sagging, dry skin and even skin cancer. Sunscreen contains chemicals that absorb UV radiation before they penetrate your skin.

29. Crest
Ozone is found in the Earth’s outer atmosphere and it protects us from most of the sun’s UV radiation.

30. Ozone is produced naturally through photochemical reactions and electric discharge reactions (lightning) in the atmosphere.

31. Ozone depletion is caused by chemicals (CFC) that break down ozone
Ozone depletion is caused by chemicals (CFC) that break down ozone. These chemicals are found in hair sprays, refrigerants etc.

32. X-RAYS
X-rays have shorter wavelength and
higher frequency
than UV radiation.
They possess enough energy to penetrate dense objects like skin and muscles.

33. X-RAYS
When X-rays hit more dense objects they are absorbed.
X-rays are used to scan luggage and packages without opening
them at the
airport.

34. GAMMA RAYS
Have the highest frequency and are the most penetrating.
Gamma rays are
emitted
from the nuclei of
radioactive atoms.

35. GAMMA RAYS
Earth receives some gamma rays from space.
They can be used to kill cancerous cells.

36. GAMMA RAYS
People using gamma radiation for treatment suffer side affects like nausea, hair loss, and fatigue because healthy cells are also damaged.