1. 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

2. Phys 150 Lecture 162 Announcements Homework 10 is due on Sunday, April 7 at midnight. Quiz on Chapter 10 on Tuesday, April 9

3. Phys 150 Lecture 183 i>clicker question The center of our galaxy is best viewed with A.visible light B.ultraviolet radiation C.infrared radiation D.All of the above

4. Phys 150 Lecture 184 i>clicker question The center of our galaxy is best viewed with A.visible light B.ultraviolet radiation C.infrared radiation – longer wavelength, diffracts around dust particles D.All of the above

5. Phys 150 Lecture 185

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7. 7 IR ≈ 1 – 1000 μm ( = 1 mm) IR viewerRipple tank

8. Phys 150 Lecture 188 Electromagnetic spectrum

9. Phys 150 Lecture 189 i>clicker question Which of the following stars is the hottest? A.Sun B.Betelgeuse (redish) C.Vega (bluish) D.They have roughly the same temperature

10. Phys 150 Lecture 1810 i>clicker question Which of the following stars is the hottest? A.Sun B.Betelgeuse (redish) C.Vega (bluish) – shortest wavelength D.They have roughly the same temperature -T = 3000/L -T in Kelvin -L in μm Lamp spectrum Thermal radiation

11. Phys 150 Lecture 1811 Courtesy of PHET

12. Phys 150 Lecture 1812 i>clicker question The amount of power radiated per square meter on the Sun’s surface compared to the filament of an incandescent light bulb is bigger by a factor of A.6000/2500 ≈ 2.4 B.(6000/2500) 2 ≈ 5.8 C.(6000/2500) 4 ≈ 33 D.(6000/2500) 8 ≈ 1100

13. Phys 150 Lecture 1813 i>clicker question The amount of power radiated per square meter on the Sun’s surface compared to the filament of an incandescent light bulb is bigger by a factor of A.6000/2500 ≈ 2.4 B.(6000/2500) 2 ≈ 5.8 C.(6000/2500) 4 ≈ 33 D.(6000/2500) 8 ≈ 1100 - Power/Area ~ T 4

14. Phys 150 Lecture 1814 i>clicker question Which of these emits heat radiation? A.Fluorescent light bulb B.Laser C.Universe D.Microwave oven

15. Phys 150 Lecture 1815 i>clicker question Which of these emits heat radiation? A.Fluorescent light bulb B.Laser C.Universe – Cosmic Microwave Background (CMB) D.Microwave oven

16. Phys 150 Lecture 1816 i>clicker question Ultraviolet (UV) radiation A.can cause skin cancer. B.can kill microorganisms. C.can cause things to glow. D.All of the above.

17. Phys 150 Lecture 1817 i>clicker question Ultraviolet (UV) radiation A.can cause skin cancer – wear sunscreen B.can kill microorganisms – purify water C.can cause things to glow – fluorescence, phosphorescence D.All of the above. Black light

18. Phys 150 Lecture 1818 i>clicker question The ozone layer A.is destroyed by UV radiation B.is created by CFC’s C.is within the stratosphere D.All of the above.

19. Phys 150 Lecture 1819 i>clicker question The ozone layer A.is destroyed by UV radiation - created B.is created by CFC’s - destroyed C.is within the stratosphere – just above the tropopause D.All of the above.