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Transcript
Lesson 16: Electromagnetic Radiation! ! Part 1: EMR! ! Electromagnetic radiation comes in the form of waves that carry energy in the form of electric and magnetic fields through space. Electromagnetic radiation is often shorted to EMR or EM waves. ! ! EM waves are produced when a charged particle is accelerated.! ! ! ! ! ! ! ! ! ! ! Electromagnetic waves are transverse waves made up of perpendicular electric and magnetic fields. ! ! Transverse means:! ! ! ! ! The wavelength of a transverse wave is from peak to peak:! ! ! ! ! ! ! ! Wavelength:!! ! ! ! The frequency of a wave is:! ! ! ! Frequency: ! ! ! ! ! ! ! ! Symbol:! Unit:! ! ! ! ! ! ! ! Symbol:! Unit:! Wave equation:! ! ! ! ! ! ! ! Speed of light:! ! ! ! ! ! ! ! Example: Red light has a wavelength of 750 nm. What is the frequency of red light?! ! ! ! ! ! ! ! ! ! ! ! Part 2: The Electromagnetic Spectrum! ! The electromagnetic spectrum is the full range of all possible frequencies of EMR. Visible light is just a tiny part of the EM spectrum. The rainbow of colours that we can see is found in the middle with wavelengths ranging from 750 nm to 400 nm. ! ! ! ! ! ! Radiowaves! ! Wavelength, frequency, energy Method of production Uses !! !! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Microwaves! ! Wavelength, frequency, energy Method of production Uses Problems ! ! !! !! !! !! !! ! Infrared! Wavelength, frequency, energy Method of production Uses Problems ! Visible! Wavelength, frequency, energy Method of production ! !! ! !! !! ! !! ! ! !! The visible light spectrum Red !! ! ! Ultraviolet! Wavelength, frequency, energy Method of production Uses Problems ! ! !! !! !! !! !! ! Orange Yellow !! Green Blue Violet! ! X-rays! Wavelength, frequency, energy Method of production Uses Problems ! !! !! ! !! ! !! !! ! Gamma Radiation! Wavelength, frequency, energy Method of production Uses Problems ! ! ! ! ! ! ! ! ! ! ! ! ! !! !! ! !! ! !! !! Practice Problems:! ! 1.! What is the fundamental origin of all EMR?! ! 2.! If a charge undergoes simple harmonic oscillations, what is the relationship between the frequency of oscillation and the frequency of the EMR produced?! ! ! 3.! What is the speed of all EMR?! 4.! Draw a sketch of an EM wave.! 5.! Which types of radiation are caused by:! A.! oscillations in circuits.! B.! transitions of valence electrons.! C.! Sudden acceleration of high-energy electrons! D.! radioactivity.! ! ! 6.! ! 7.! ! 8.! ! 9.! ! 10.! ! 11.! ! Why is a car’s radio reception often distorted when a car is driving near high-voltage transmission lines or under steel-reinforced concrete?! An electromagnetic wave is travelling straight up perpendicular to the Earth’s surface. If its electric field is oscillating in an east-west plane, what is the direction of oscillation for the magnetic field?! Calculate the quantity indicated for each of the following electromagnetic waves:! A.! The frequency of a 1.8 cm microwave. (1.7 x 1010 Hz)! B.! The wavelength of a 3.2 x 1010 Hz radar signal. (9.4 mm)! C.! The distance between adjacent maxima of magnetic field strength in the electromagnetic wave coming from a 60 Hz transmission line. (5.0 x 106 m)! D.! The frequency of red visible light of wavelength 650 nm. (4.6 x 1014 Hz)! Two football fans are listening to a Grey Cup game on radio, one in Montreal where it is being played, and the other in the Northwest Territories, 6000 km away. The distant signal is transmitted by microwaves using a communications satellite at an altitude of 36000 km. Making whatever assumptions seem reasonable, determine how much sooner the fan in Montreal hears the results of any play. (0.24 s)! What is the wavelength of a certain EMR that has a period of 5.65 x 10-11 s? (0.0170 m)! A planet is 7.60 x 1012 m from Earth. How long will it take a radio signal to travel to this planet and back? (5.07 x 104 s)! 12.! Explain in general terms why x-rays and gamma rays are especially likely to cause cancers in the cells of the skin, bone marrow and intestinal lining.! ! ! ! ! ! ! ! ! ! ! The Electromagnetic Spectrum Type of EMR Radio and Radar Frequency Range: ! Wavelength Range: Microwaves Frequency Range: ! Wavelength Range: Infrared Frequency Range: ! Wavelength Range: Visible Frequency Range: ! Wavelength Range: Ultraviolet Frequency Range: ! Wavelength Range: X Ray Frequency Range: ! Wavelength Range: Gamma Frequency Range: ! Wavelength Range: Cosmic Frequency Range: ! Wavelength Range: How it is produced What it is used for Problems Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________ Cancer Burns Mutations Radiation sickness Death Other: ________
