17 2 waves of the electromagnetic spectrum
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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