RADIATION and the EM Spectrum

Transcription

1 RADIATION and the EM Spectrum Radioactivity is the of high-energy particles and/or of energy from a substance as a result of of its atoms. There are several types of radiation. Radiation from the sun is an example of ELECTROMAGNETIC radiation. Electromagnetic radiation (EMR) is... ENERGY IN THE FORM OF ELECTROMAGNETIC WAVES, SENT OUT IN ALL DIRECTIONS The sun produces many types of EMR. These include:,,,,, and. Electromagnetic radiation can be pictured as a series of waves that spread outward from a source (like waves on a pond). But, water waves are made up of (water particles) while an electromagnetic wave is composed of changing electric and magnetic fields that travel at the. These changes are produced by the vibrations of a charged particle. [ 300,000,000 m/s ] A closer look at electromagnetic waves... : The number of wavelengths that pass a point in one second. Measured in hertz. 1 hertz = 1 cycle/second : The distance from a point on one wave to the same point on the next wave. Measured in meters These two terms are related to one another in that if the frequency of a wave, the wavelength. For example:

2 Electromagnetic radiation is classified (named) based on their frequency and wavelength. For example: Low frequency and long wavelength = RADIO WAVES High frequency and short wavelength = GAMMA RAYS When the types of EMR are arranged from LOW to HIGH frequency they show the. The of electromagnetic radiation is also related to its frequency... Where... low frequency = energy & high frequency = energy Notice how the most energetic rays are unable to penetrate the Earth s atmosphere. This is good news for us as they are also the most hazardous to living tissues. VISIBLE LIGHT: ranges from about 400 nanometers to about 700 nanometers (1 nm = m) Each colour has its own wavelength. o o Red has the wavelength Violet has the wavelength When all the wavelengths are seen together they make.

3 When white light shines through a PRISM (as seen below), the white light is broken apart into the colors of the visible light spectrum. Water vapor or droplets in the atmosphere can also break apart wavelengths creating a. Our are receivers for these tiny visible light waves. The is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light wavelength(s) it. All other colors are absorbed. Because we can only see things in visible light, this restricts the size of the objects we can see. In order for our eyes to form an image of something, that object needs to be than the wavelength of light used to see it. For example, we are unable to see the molecules that make up our desks (even though we know they are there) because those molecules are smaller than the waves in the visible spectrum; therefore we cannot tell that they are there. Is Radiation always harmful? PROs of Electromagnetic Radiation We can detect listen to music at home or in the car using a that detects. We can heat food quickly using. You can take a photograph of your bones using. CONs of Electromagnetic Radiation The effect of ultraviolet radiation on the skin can be a. Exposure to harmful radiation can cause damage to your cells and cause them to undergo uncontrolled cell division which leads to a. Natural Background Radiation - generally harmless to living organisms, but everywhere! All radioactive substances that occur naturally in organic matter emit some natural background radiation. o Includes radiation from: Low energy ( frequency, wavelength) electromagnetic radiation. Ionizing Radiation this is the one to watch out for! This is the type of radiation that has high enough energy ( frequency, wavelength) to cause damage to living tissues. Has enough energy to knock electrons out of atoms (creating ions). Potentially harmful to all cells, but most dangerous to cells that are developing or multiplying, such as reproductive cells, blood forming cells in the bone marrow, intestinal or fetal cells. Dangers include (vomiting, diarrhea, nausea, appetite loss), cancer (cells divide uncontrollably), and (miscoded genetic material).

4 Electromagnetic Radiation Questions 1. In the EM spectrum, visible light is divided up into the seven different colours. a. List the colours in order form longest wavelength to shortest wavelength. b. What is an easy way for you to remember the order of the colours? Blue light UV Infrared Red Light Yellow Light X-rays Microwaves Radio waves Gamma rays 2. Arrange the above types of electromagnetic radiation according to a. Increasing energy (E). (i.e. lowest to highest) b. Decreasing frequency (f). (i.e. highest to lowest) c. Increasing wavelength (λ). (i.e. shortest to longest) 3. Consider four types of electromagnetic radiation: A has a wavelength of 2m B has a wavelength of 10 cm C has a wavelength of 700 nm D has a wavelength of 250 nm a) Which has the longest wavelength? b) Which has the highest frequency? c) Which has the lowest energy? d) Which has the shortest wavelength? e) Which has the lowest frequency? f) Which has the highest energy? 4. Use a ruler to measure the wavelength of each diagram. A - cm B - cm C - cm Which wave diagram (A,B,C) has the lowest frequency? Which wave diagram (A,B,C) would have the highest energy? 5. What kind of EMR could be used to see small protozoa? Atoms? 6. Some insects, like bees, can see light of a shorter wavelength than humans can. What kind of radiation do you think a bee sees

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