17.2 Waves of the electromagnetic Spectrum

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# 17.2 Waves of the electromagnetic Spectrum - PowerPoint PPT Presentation

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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### 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
• 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 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 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 are the electromagnetic waves with the longest wavelengths and lowest frequencies
• There are two types of Radio Waves:
• 2. Microwaves
• They carry signals for both radio and television programs
• 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
• Microwaves are radio waves with the shortest wavelengths and highest frequencies.
• Microwaves have many uses
• Cellular phones, cooking, and radar
• 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 are electromagnetic waves with wavelengths shorter than those of radio waves
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
• 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 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 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
• 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
• 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-Rays
• 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
• 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 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
• 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
• 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