1. Electromagnetic Spectrum

2. Electromagnetic waves
are waves that can travel through matter or empty space where matter is not present.
longer the wavelength, the lower the energy of the wave.

4. Electromagnetic Spectrum
Low frequency, long wavelength, lowest energy
used for communication, such as radios, tv
Higher frequency radio waves
Used in Radar and cell phones.
Radio
Wave
Microwaves

5. Infrared Waves Infra - Infrared Radiation means before
frequencies lower than red on the visible spectrum, thereby having longer wavelengths and less energy than red wavelengths.
All objects emit infrared radiation, and hotter objects emit more infrared radiation than cooler objects.
Used to keep food warm, or cook food, like a toaster

6. Infrared Waves Continued
Infrared Radiation
Heat energy is transmitted by infrared radiation.
Infrared is absorbed = warmer

7. Electromagnetic Spectrum
Visible light is the range of electromagnetic waves that can be detected by the human eye.
The entire range of visible light is called the visible light spectrum.
The wavelengths of visible light are in the middle range of wavelengths/frequencies of electromagnetic waves.
Visible light

8. Visible Light Continued
The human eye reacts to different energies and frequencies of light so that different colors are seen.
Higher frequencies (shorter wavelengths) are perceived as colors toward the blue-violet range and have higher energy.
Lower frequencies (longer wavelengths) are perceived as colors toward the orange-red range and have lower energy.

9. Ultraviolet Radiation (UV)
Ultraviolet Waves
frequencies higher than violet
Damages skin and eyes due to high frequency.
Helps the skin produce vitamin D
Seen by bees

10. EMS X-rays Gamma Higher frequencies and energies
Produced by the Sun and other stars.
Pass through soft tissue but absorbed by more dense material.
Most harmful ray.
Produced by radioactive substances, the sun and other stars.
Kills normal cells but can also be used to fight cancerous tumors.

11. Interaction of Light Waves
Transmission Absorption
The passage of an EM wave through a medium.
The disappearance of an EM wave into the medium.

12. Interaction of Light Waves
Transparent
Translucent
most of the light passes through. Ex. Air, water, clear glass. Uses: light bulbs, clock faces
transmit some light but they also cause it to spread out in all directions. You can see light through translucent materials but cannot see objects clearly. Ex. frosted windows, notebook paper.

13. Interaction of Light Waves
Opaque
No light passes through
Reflect light, absorb light, or both. Ex. Wood, mirrors, metal, fabric

14. Why we see color Color White Black
Is determined by the wavelength being absorbed or reflected.
An object is the color it reflects.
Ex. A shirt that is red is reflecting the red wavelength but absorbing all others.
Reflects all colors in visible light.
Absorbs all colors in visible light.

15. Why we see color Colored Filters
allow only certain colors of light to pass/transmit through them; they absorb or reflect all other colors. Ex. a blue filter only transmits blue light. Objects seen through a blue filter will look blue if the objects reflect blue; objects of other colors will appear black because the other color wavelengths are being absorbed by the filter.
Let’s experiment with filters:
Colored Filters