# hwsol2 - Physics 31 Spring 2007 Solution to HW#2 Problem A...

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Unformatted text preview: Physics 31 Spring, 2007 Solution to HW #2 Problem A Use the first order Taylor approximation (1 + ) n ≈ 1 + n (for 1) to simplify the following ex- pressions for the indicated limiting cases: (a) M − m M + m for m M (b) 1 λ − 1 λ + ∆ λ for ∆ λ λ (c) p p 2 c 2 + m 2 c 4 for p mc For part (a), M − m M + m = M ³ 1 − m M ´ M ³ 1 + m M ´ = ³ 1 − m M ´³ 1 + m M ´ − 1 ≈ ³ 1 − m M ´³ 1 − m M ´ ≈ 1 − 2 m M For part (b), 1 λ − 1 λ + ∆ λ = 1 λ − 1 λ µ 1 + ∆ λ λ ¶ = 1 λ " 1 − µ 1 + ∆ λ λ ¶ − 1 # ≈ 1 λ · 1 − µ 1 − ∆ λ λ ¶¸ = ∆ λ λ 2 For part (c), as we did in class, p p 2 c 2 + m 2 c 4 = m 2 c 4 µ 1 + p 2 c 2 m 2 c 4 ¶ = mc 2 · 1 + p 2 m 2 c 2 ¸ 1 / 2 ≈ mc 2 · 1 + 1 2 p 2 m 2 c 2 ¸ = mc 2 + p 2 2 m 2 –16 Light of wavelength 400 nm is shone on a metal sur- face in an apparatus like that of Fig. 2.9. The work function of the metal is 2.50 eV. (a) Find the extinction voltage, that is, the retarding voltage at which the photoelectron current...
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## This note was uploaded on 02/29/2008 for the course PHYSICS 31 taught by Professor Hickman during the Spring '07 term at Lehigh University .

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hwsol2 - Physics 31 Spring 2007 Solution to HW#2 Problem A...

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