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Lecture

# Atomic radiation, photon energy, X rays

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School
Department
Physics
Course
PH 122
Professor
Brian Jones
Semester
Spring

Description
28 March What are the photon energies corresponding to the following wavelengths? 1240 E (in eV) = λ(¿nm) Near IR, 1000 nm 1.24 eV Far red end of the spectrum, 750 nm 1.65 eV Far blue end of the spectrum, 400 nm 3.1 eV Near UV, 290 nm 4.28 eV Atomic Radiation Q = eσAT 4 ∆t σ = 5.67 x 10 W/(m K ) 4 Visible spectrum: approx.. 400 – 750 nm Peak intensity shifts to shorter wavelengths as the temperature increases. 6 2.9x10 nmK λpeak(in nm) = T Wien’s law for the peak wavelength of a thermal emission spectrum A typical incandescent lamp has a filament at a temperature of approximately 2500 °C. What is the peak wavelength of the emission? Temp in K = 2500 + 273 = 2773 K 6 2.9x10 nmK 2773K 980 nm Visible Light, Near IR and UV The three different types of cones have different color sensitivities. The band gap of the silicon used to make the CCD detector in a black and white security camera is 1.12 eV. Photons with energy greater than this will be detected. What wavelength does this correspond to? 1240 1.12 eV = λ
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