Modern Physics
2nd Edition
ISBN: 9780805303087
Author: Randy Harris
Publisher: Addison Wesley
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Question
Chapter 3, Problem 11E
(a)
To determine
The Planck’s spectral energy density in the limit of small frequencies.
(b)
To determine
The Planck’s spectral energy density at high frequencies.
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Students have asked these similar questions
Determine lm , the wavelength at the peak of the Planck distribution, and the corresponding frequency ƒ, at these temperatures: (a) 3.00 K; (b) 300 K; (c) 3000 K.
Planck's radiation law can be written
ux
=
8лhc 1
25 eßhc/2-1
Show that the wavelength corresponding to the maximum energy density of the
radiation fulfills the condition
λmax T
=
.
constant
What is this constant? (This result is known as Wien's transition law.) Tip: you can
solve the constant approximation by e.g. iterating an equation of the form
Xn = 5 (1-e¯Xn-1)
with a suitable initial value x1.
The wavelength λmax at which the Planck distribution is a maximum can be found by solving dρ(λ,T)/dT = 0. Differentiate ρ(λ,T) with respect to T and show that the condition for the maximum can be expressed as xex − 5(ex − 1) = 0, where x = hc/λkT. There are no analytical solutions to this equation, but a numerical approach gives x = 4.965 as a solution. Use this result to confirm Wien’s law, that λmaxT is a constant, deduce an expression for the constant, and compare it to the value quoted in the text.
Chapter 3 Solutions
Modern Physics
Ch. 3 - Prob. 1CQCh. 3 - Prob. 2CQCh. 3 - Prob. 3CQCh. 3 - Prob. 4CQCh. 3 - Prob. 5CQCh. 3 - Prob. 6CQCh. 3 - Prob. 7CQCh. 3 - A ball rebounds elastically from the floor. What...Ch. 3 - Prob. 9CQCh. 3 - Prob. 10CQ
Ch. 3 - Prob. 11ECh. 3 - Prob. 12ECh. 3 - Prob. 13ECh. 3 - Prob. 14ECh. 3 - Prob. 15ECh. 3 - Prob. 16ECh. 3 - Prob. 17ECh. 3 - What is the stopping potential when 250 nm...Ch. 3 - Prob. 19ECh. 3 - Prob. 20ECh. 3 - Prob. 21ECh. 3 - Prob. 22ECh. 3 - Prob. 23ECh. 3 - Prob. 24ECh. 3 - Prob. 25ECh. 3 - Prob. 26ECh. 3 - Prob. 27ECh. 3 - Prob. 28ECh. 3 - Prob. 29ECh. 3 - Prob. 30ECh. 3 - Prob. 31ECh. 3 - Prob. 32ECh. 3 - Prob. 33ECh. 3 - Prob. 34ECh. 3 - Prob. 35ECh. 3 - Prob. 36ECh. 3 - Verify that the Chapter 2 formula KE=mc2 applies...Ch. 3 - Prob. 38ECh. 3 - Prob. 39ECh. 3 - Prob. 40ECh. 3 - Prob. 41ECh. 3 - Prob. 42ECh. 3 - Prob. 43ECh. 3 - Prob. 44ECh. 3 - Prob. 45ECh. 3 - Prob. 46ECh. 3 - Prob. 47CECh. 3 - Prob. 49CECh. 3 - Prob. 50CECh. 3 - Prob. 51CECh. 3 - Prob. 52CECh. 3 - Prob. 53CECh. 3 - Prob. 54CECh. 3 - Prob. 55CE
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- (a) A vacuum photocell is sequentially illuminated with light of different wavelengths 2. A voltmeter is used to determine that there is a different voltage between the cathode and the anode. V (iii) Determine a relation for Planck's constant in terms of pairs of voltage measurements at different wavelengths such that W₁ cancels out. (iv) Evaluate Planck's constant for the following pair of measurements: measurement 1 finds = 447 nm and V=635 mV, and measurement 2 finds = : 502 nm and V=339 mV.arrow_forward(a) Calculate the speed of an electron that is in the n = 1 orbit of a hydrogen atom, and give your answerv as a fraction of the speed of light in empty space c, for example, v = 0.5 if the answer werev = c/2 = 1.50 × 108 m/s. (It isn’t.)(b) How many nanometers would be the wavelength of the photon emitted when the electron in a hydrogenatom jumps from the n = 3 orbit to the n = 2 orbit? This is the Hα line, and its light is scarlet, the color offresh human blood.(c) How many nanometers would be the wavelength of the photon emitted when the electron in a hydrogenatom jumps from the n = 2 orbit to the n = 1 orbit?(d) How many nanometers would be the wavelength of a photon that would have the minimum amount ofenergy needed to ionize any hydrogen atom? (Hint: Electromagnetic radiation with this wavelength or shorteris called extreme ultraviolet radiation.(e) How many electron-volts (eV) would the electron in part (7)(d) need to have?arrow_forward(2.13) Selection rules in hydrogen Hydrogen atoms are excited (by a pulse of laser light that drives a multi-photon process) to a spe- cific configuration and the subsequent spontaneous emission is resolved using a spectrograph. Infra- red and visible spectral lines are detected only at the wavelengths 4.05 um, 1.87 µm and 0.656 µm. Explain these observations and give the values of n and l for the configurations involved in these transitions.arrow_forward
- Calculate the De-Broglie wavelength for, A biological virus of size d is 10 nm – 300 nm, mass m is 10 ^ -15 kg and average speed v = 1 mm/s. An atomic electron size of d is 2.8 fm, mass m is 9.1 x 10^-31 kg, and in orbital speed in first Bohr orbit is v= 2.6 x 10^6 m/sarrow_forward(b) (deBroglie wave length) Determine the deBroglie wavelength (formula: p=h/2) of a grain of dust with diameter 1um, density 1kg m-3 and speed 1cm s. Compare your result with the diameter of the dust grain and the diameter of an atom. Comment?arrow_forwardFor the thermal radiation from an ideal blackbody radiator with a surface temperature of 2000 K, let Ic represent the intensity per unit wavelength according to the classical expression for the spectral radiancy and IP represent the corresponding intensity per unit wavelength according to the Planck expression.What is the ratio Ic/IP for a wavelength of (a) 400 nm (at the blue end of the visible spectrum) and (b) 200 mm (in the far infrared)? (c) Does the classical expression agree with the Planck expression in the shorter wavelength range or the longer wavelength range?arrow_forward
- Atoms have quantized energy levels similar to those of Planck’s oscillators, although the energy levelsof an atom arePage 2 of 2usually not evenly spaced. When an atom makes a transition between states separated in energy by DE,energy is emitted in the form of a photon of frequency f . Although an excited atom can radiate at anytime from t= 0 to t =infinity, the average time interval after excitation during which an atom radiates iscalled the lifetime Ʈ. If Ʈ =1.0 × 10-8 s, use the uncertainty principle to compute the line width Δ fproduced by this finite lifetime.arrow_forwardGiven this quantum state: ¥(r,0,0) = R(r)(√₂Y+Y¹-Y₂²), a) measured: |Z|² , find possible outcomes, corresponding probabilities and the average value b) repeat the same but instead with measured say Lz c) If you had first measured Lz to be planck's constant, and then measured |Z|² what can be said about the result of |Z|² ?arrow_forwardOutline the steps leading to the formula for the number of photons with angular fre- quencies between w and w + dw in blackbody radiation at a temperature T: w? dw V n(w)dw = 2 x 272c3 ehw/kBT Show that n(w) has a peak at a frequency given by w = 1.59kgT/h. Show further that the spectral energy densities ux and uw peak at Amax = hc/(4.97KBT) and wmax = 2.82KBT/ħ, respectively.arrow_forward
- In a photoelectric experiment it is found that a stopping potential of 1.00 V is needed to stop all the electrons when incident light of wavelength 225 nm is used and 1.5 V is needed for light of wavelength 207 nm. From these data determine Planck's constant. (Enter your answer, in eV s, to at least four significant figures.) 4.2367e-15 X ev s From these data determine the work function (in eV) of the metal. 4.6 X evarrow_forward(b) Calculate the de Broglie wavelength of an electron having a mass of 9.11 x 10-31 kg and a charge of 1.602 x 10-19 J with a Kinetic energy of 110 eV. The value of the Planck’s constant is equal to 6.63 * 10-34 Js.arrow_forwardFor a temperature of 5800 K (the sun’s surface temperature), fi nd the wavelength for which the spectral distribution calculated by the Planck and RayleighJeans results differ by 5%.arrow_forward
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