Phys 150 Lecture 71 Please sit together in pairs: –Onyema and Erica –Alejandra and John W. –Chris and Dian –Ryan and Michael –John F. and Honglu –Walter and Matt –Max and Lin –Amanda and Anwen –Pauline and Mengyue –Jennifer and Melissa –Alexandra and Erich –David and Irfan –Abigael and Jason –Jake and Jiayuan

Phys 150 Lecture 162 Announcements Homework 10 is due on Sunday, April 7 at midnight. Quiz on Chapter 10 on Tuesday, April 9 Exam 2 is Thursday, April 18 in class. Covers Chapters 6-10.

Phys 150 Lecture 193 Electromagnetic spectrum

Phys 150 Lecture 194 i>clicker question Microwaves are used for A.heating water B.communications C.radar D.All of the above

5 i>clicker question Microwaves are used for A.heating water – microwave oven B.communications – cell phones, wireless C.radar – get velocity from doppler shift D.All of the above Microwave oven Phys 150 Lecture 19

6 i>clicker question Microwaves are used for A.heating water B.communications C.radar D.All of the above IR radiation = 1 μm – 1 mm Microwaves = 1 mm – 1 m Radio waves = 1 m and beyond

Phys 150 Lecture 197 i>clicker question This device is used for A.missle guidance B.radar tracking C.communications D.crowd control

Phys 150 Lecture 198 i>clicker question This device is used for A.missle guidance B.radar tracking C.communications D.crowd control -Active Denial System (ADS) -Microwaves (3 mm) heat water in skin -Has never been used

Phys 150 Lecture 199 i>clicker question Calculate the wavelength of WILL FM 90.9 radio (90.9 MHz) A.3 m B.30 m C.300 m D.3000 m c = 3 x 10 8 m/sec

Phys 150 Lecture 1910 i>clicker question Calculate the wavelength of WILL FM 90.9 radio (90.9 MHz) A.3 m B.30 m C.300 m D.3000 m c = 3 x 10 8 m/sec L = c/f = (3 x 10 8 m/sec) / (90.9 x 10 6 /sec) ≈ 3 m

Phys 150 Lecture 1911 i>clicker question Calculate the wavelength of WILL AM 580 radio (580 kHz) A.5 m B.50 m C.500 m D.5000 m

Phys 150 Lecture 1912 i>clicker question Calculate the wavelength of WILL AM 580 radio (580 kHz) A.5 m B.50 m C.500 m D.5000 m c = 3 x 10 8 m/sec L = c/f = (3 x 10 8 m/sec) / (580 x 10 3 /sec) ≈ 500 m

Phys 150 Lecture 1913 i>clicker question This airport full-body scanner uses A.microwaves B.radio waves C.ultraviolet radiation D.infrared radiation

Phys 150 Lecture 1914 i>clicker question This airport full-body scanner uses A.microwaves B.radio waves C.X rays D.infrared radiation -Millimeter wave scanner -Uses reflected microwaves

Phys 150 Lecture 1915 i>clicker question X rays (choose the INCORRECT answer) A.are preferentially absorbed by light elements B.can be reflected C.can cause cancer D.are used in CT scans

Phys 150 Lecture 1916 i>clicker question X rays (choose the INCORRECT answer) A.are preferentially absorbed by light elements - Absorbed by heavy elements B.can be reflected – X ray backscatter C.can cause cancer – depends on dose (Sieverts) D.are used in CT scans – CAT scans

Phys 150 Lecture 1917 i>clicker question X rays (choose the INCORRECT answer) A.are preferentially absorbed by light elements - Absorbed by heavy elements B.can be reflected – X ray backscatter C.can cause cancer – depends on dose (rems) D.are used in CT scans – CAT scans X ray backscatter at O’Hare

Phys 150 Lecture 1918 i>clicker question X rays (choose the INCORRECT answer) A.are preferentially absorbed by light elements - Absorbed by heavy elements B.can be reflected – X ray backscatter C.can cause cancer – depends on dose (rems) D.are used in CT scans – CAT scans

Phys 150 Lecture 1919 i>clicker question MRI uses A.microwaves B.radio waves C.X rays D.infrared radiation

Phys 150 Lecture 1920 i>clicker question MRI (Magnetic Resonance Imaging) uses A.microwaves B.radio waves – and a strong magnetic field C.X rays D.infrared radiation Magnetic field

Phys 150 Lecture 1921 i>clicker question A PET scan A.is a type of CAT scan B.uses X rays C.uses gamma rays D.uses ultrasound

Phys 150 Lecture 1922 i>clicker question A PET scan (Positron Emission Tomography) A.is a type of CAT scan – Computed Tomography B.uses X rays – CT scan C.uses gamma rays – positrons annihilate electrons to produce gamma rays D.uses ultrasound – mm wavelength sound