17 2 waves of the electromagnetic spectrum
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17.2 Waves of the electromagnetic Spectrum - PowerPoint PPT Presentation

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17.2 Waves of the electromagnetic Spectrum . Pg. 578 - 585. What is the Electromagnetic Spectrum? . All electromagnetic waves travel at the same speed in a vacuum, BUT they have different wavelengths at different frequencies

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What is the electromagnetic spectrum
What is the Electromagnetic Spectrum?

  • All electromagnetic waves travel at the same speed in a vacuum, BUT they have different wavelengths at different frequencies

  • Visible Light: Is radiation in the wavelengths that your eyes can see

    • Only a small portion of electromagnetic radiation is visible light

    • The rest of the wavelengths are invisible

What is the electromagnetic spectrum1
What is the Electromagnetic Spectrum?

  • Recall how speed, wavelength, and frequency are related

    • Speed = Wavelength X Frequency

  • As the wavelength decreases, the frequency increases

    • Waves with the longest wavelength have the lowest frequencies

    • Waves with the shortest wavelength have the highest frequencies

    • **The higher the frequency, the higher its energy

What is the electromagnetic spectrum2
What is the Electromagnetic Spectrum?

  • The Electromagnetic Spectrum is the complete range electromagnetic waves placed in order of increasing frequency

  • The Order:

  • Radio Waves, Infrared Rays, Visible Light, Ultraviolet Light, X-rays, and Gamma Rays

Radio waves
Radio Waves

  • Radio Waves are the electromagnetic waves with the longest wavelengths and lowest frequencies

  • There are two types of Radio Waves:

    • 1. Broadcast Waves (Radio and TV)

    • 2. Microwaves

Broadcast waves
Broadcast Waves

  • Radio waves with longer wavelengths are used in broadcasting

  • They carry signals for both radio and television programs

How broadcast waves work
How Broadcast Waves Work

  • A broadcast station sends out radio waves at certain frequencies

  • A radio or TV antenna picks up the waves and converts the radio signals into electrical signals

    • Inside radios the electrical signals are converted into sound

    • Inside TVs the signal is converted into sounds and pictures


  • Microwaves are radio waves with the shortest wavelengths and highest frequencies.

  • Microwaves have many uses

    • Cellular phones, cooking, and radar


  • Radar stands for Radio Detection And Ranging

  • Radar is a system that uses reflected radio waves to detect objects and measure their distance and speed


  • To measure distance:

    • A radar device sends out radio waves that reflect off an object

    • The time it takes for the reflected waves to return is used to calculate the object’s distance

  • To measure speed:

    • A radar device uses the Doppler effect

    • The difference in frequency is used to calculate the car’s speed

Infrared rays
Infrared Rays

  • Infrared Rays are electromagnetic waves with wavelengths shorter than those of radio waves

Heat lamps
Heat Lamps

  • Infrared rays have more energy than radio waves

  • You feel the energy of infrared rays as heat

  • Heat lamps have bulbs that give off mostly infrared rays and very little visible light

    • Heat lamps are used to keep food warm or heat up rooms quickly

Infrared cameras
Infrared Cameras

  • Most objects give off some infrared rays

    • Warmer objects give off infrared rays with more energy and higher frequencies

  • Infrared cameras take pictures using infrared rays instead of light

    • These pictures are called thermograms, which is an image that shows regions of different temperatures in different colors

    • Used by firefighters to locate people during fires

Visible light1
Visible Light

  • Visible light are electromagnetic waves that we can see

  • Visible light has shorter wavelengths and higher frequencies than infrared rays

    • Visible light with the longest wavelength appear red

    • Visible light with the shortest wavelength appear violet in color

Ultraviolet rays
Ultraviolet Rays

  • Ultraviolet Rays are electromagnetic waves with wavelengths shorter than those of visible light

  • Ultraviolet Rays have higher frequencies than visible light so they have more energy

    • Have enough energy to damage or kill living cells

    • Ultraviolet lamps are used to kill bacteria on hospital equipment

Ultraviolet rays and health
Ultraviolet Rays and Health

  • Small doses of ultraviolet rays are useful!

    • Cause skin to produce vitamin D, which is needed for healthy bones and teeth

  • Large doses of ultraviolet rays can be harmful!

    • Can burn your skin, which causes skin cancer and damage to your eyes

    • By applying sun block and wearing sunglasses you can limit the damage caused by ultraviolet rays

X rays

  • X-Rays are electromagnetic waves with wavelengths just shorter than those of ultraviolet rays

  • X-Rays have higher frequencies than ultraviolet rays = more energy

  • X-Rays have so much energy they can penetrate most matter except bone

    • Bones absorb X-rays

How x rays work
How X-Rays Work

  • Bones absorb X-rays and does not allow them to pass through

  • X-rays pass through skin and soft tissue, causing the photographic film in the X-ray machine to darken when it is developed

  • Bones absorb the X-rays and appear as the lighter areas on the film

X rays1

  • Too much X-ray exposure can cause cancer

    • When X-rays are taken a lead apron is worn during the procedure

    • The lead apron absorbs the X-rays and prevents them from reaching your body

Uses of x rays
Uses of X-Rays

  • X-rays are sometimes used in industry and engineering

    • Used to find out if steel has any tiny cracks because the X-rays will pass through the tiny cracks that are not visible to the human eye

    • Used to check the quality of joints in oil and gas pipelines

Gamma rays
Gamma Rays

  • Gamma Rays are electromagnetic waves with the shortest wavelengths and highest frequencies

  • Gamma Rays have the most energy

    • Are the most penetrating of all of the electromagnetic waves

Uses of gamma rays
Uses of Gamma Rays

  • Radioactive substances and nuclear reactions produce gamma rays

  • Gamma rays are also used in medicine

    • Used to kill cancer cells inside the body

    • Used to examine internal body structures

      • A patient will be injected with fluid that emits gamma rays

      • The gamma ray detector can form an image of the inside of the body

Gamma rays and space
Gamma Rays and Space

  • Some objects in space give off bursts of gamma rays

  • Gamma Rays are blocked by Earth’s atmosphere

    • Gamma ray telescopes that detect the gamma rays must orbit above the Earth’s atmosphere

  • Astronomers believe that explosions of stars in the distant galaxies are one way of producing gamma rays