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Waves of the Electromagnetic Spectrum
Transcript of Waves of the Electromagnetic Spectrum
Characteristics of Electromagnetic Waves
- Electromagnetic waves are waves that do NOT need a medium to travel through like mechanical waves do.
- Examples of electromagnetic waves:
(microwaves, radar, MRI)
(the rainbow of light you see- red, orange, yellow, green, blue, indigo, violet)
Characteristics of Electromagnetic Waves
- All electromagnetic waves travel at the same speed, but they have different wavelengths and different frequencies.
speed = wavelength x frequency
Look at the formula above. Since the speed of all electromagnetic waves is the same, then as the wavelength decreases the frequency must increase.
- Waves with longer wavelengths have lower frequencies
- Waves with shorter wavelengths have higher frequencies
When you switch on a microwave oven, it gives off electromagnetic waves that bounce around inside the oven, penetrating the food. Water molecules in the food absorb the energy from the microwaves, causing them to get hot. Microwaves are also used to transmit cell phone calls.
Short-wavelength microwaves are used in radar. A radar device sends out short pulses of radio waves, which are reflected by objects they strike. A receiver detects the reflected waves and measures the time it takes for them to come back. It is used to monitor airplane landing/taking off, to locate ships at sea, to measure the speed of a car or baseball.
Magnetic Resonance Imaging (MRI):
These radio waves produce pictures of muscles and tissues in the human body.
are the electromagnetic waves with the longest wavelengths and lowest frequencies.
- Antennas pick up radio waves from the air and send them through wires to your radio. The radio converts the electromagnetic waves into the sound that comes out of the radio speakers.
- Types of radio waves include: microwaves, radar, and magnetic Resonance Imaging (MRI- at the hospital it takes images of your internal organs)
The only electromagnetic waves that you can see are light.
Visible light has shorter wavelengths and higher frequencies than infrared rays (see picture).
The longest wavelengths of visible light are red. As the wavelengths decrease and the frequencies increase, you can see other colors of light (orange, yellow, green, blue, indigo and violet).
Infrared rays have shorter wavelengths and higher frequencies than radio waves (see picture).
If you switch on an electric stove, you can feel infrared rays. As something gets warmer, it gives out energy as heat. This energy is infrared radiation, or infrared rays. Because you can feel infrared rays as warmth, these rays are often called heat rays. Heat lamps give off infrared rays and people use infrared cameras to detect body heat or check their houses to see where heat is leaking out (energy leaks).
Chapter 3 Section 2
Look at all the different types of waves on the electromagnetic spectrum.
Notice how the wavelength and frequency change for each of the different types of waves.
(also called UV rays) are electromagnetic waves with wavelengths just shorter than those of visible light (see picture). UV waves have higher frequencies than visible light, so they carry more energy.
Humans can't see UV rays, but some insects can!
UV waves can be GOOD
Because the energy of UV rays is great enough to damage or kill living cells, UV lamps are used to kill bacteria on hospital equipment. Small doses of UV rays can cause human skin cells to produce vitamin D, which is needed for healthy bones and teeth.
UV waves can be BAD
Too much exposure to ultraviolet rays can cause skin cancer and damage your eyes. Sunblock and sunglasses can limit the damage to your body.
are electromagnetic waves with very short wavelengths, and a little higher frequencies than UV rays (see picture).
Because of their high frequencies, X-rays carry more energy than UV rays and can penetrate most matter.
Dense matter, such as bone, absorbs X-rays and does not allow them to pass through. For this reason, X-rays are used to make images of bones inside the body. X-rays pass right through skin and soft tissues. The photographic film darkens where skin/soft tissue is, and causes bones to show as light areas on the film. Too much exposure to X-rays can cause cancer.
Gamma rays have the shortest wavelengths and highest frequencies of the electromagnetic spectrum (see picture).
Some objects far out in space give off bursts of gamma rays, but Earth's atmosphere blocks these gamma rays from getting to us.
Gamma rays can be BAD
Some radioactive substances and certain nuclear reactions produce gamma rays. Because they have the greatest amount of energy, they are the most penetrating of all the electromagnetic waves and can cause serious illness.
Gamma rays can be GOOD
Used in controlled conditions, gamma rays have some medical uses, such as killing cancer cells in radiation therapy. Also, a patient can be injected with a fluid that emits gamma rays. Then a gamma-ray detector can form an image of the inside of the body.