The ternPerature of the skin is approximately 35.0degreeC. At what wavelength do

Question

The ternPerature of the skin is approximately 35.0degreeC. At what wavelength dots the emited from the skin reach its peak? When a certain metal is illuminated with light of frequency 3.0 times 10^15 Hz, a stopping potential of 7.0 V is required to stop the most energetic ejected electrons. What is the work function of the metal? Suppose we use radiation (A = 550 nm) to determine the position of the electron to within the wavelength of the light. What will be the resulting uncertainty in the electron's velocity?

Explanation / Answer

11)

Use the Wien displacement law.

Lambda(max) * T = -0.3 cm*K

T in this case be in Kelvin, and therefore 308 K.

L=0.00000974 m

12)

K.E. = hf - Wf

7*1.6 x 10^-19 = 6.626 x10^-34*3 x 10^15 - Wf

11.2x 10^-19 = 19.878 x 10^-19 - Wf

Wf = 8.678 x 10^-19 J

Wf =8.678 x 10^-19 / 1.6 x 10^-19 = 5.42375 eV

13)

According to the uncertainty principle,

xp h/2, so the minimum uncertainty is h/2

The uncertainty in momentum is,

p = h/(2x) = 1.05e-34/(2*550e-9) = 0.954 x 10-28 kg.m/s

p = mv

p = mv

The uncertainty in velocity would be

v = p/m = 0.954 x 10-28 /9.11e-31 = 104.72 m/s

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