Bài tập và Đáp Án câu hỏi tự luận môn vật lý 2

For a photon that is just able to dissociate a molecule of silver bromide, find a the photon energy in electron volts; b the wavelength of the photon; c the frequency of the photon.. A p

1 the light-sensitive compound on most photographic films is silver bromide, AgBr A film is “exposed” when the light energy absorbed dissociates this molecule into its atoms (The actual

process is more complex, but the quantitative result does not differ

greatly.) The energy of dissociation of AgBr is 1x105 J/mol For a photon that is just able to dissociate a molecule of silver bromide, find (a) the photon energy in electron volts; (b) the wavelength of the photon; (c) the frequency of the photon (d) What is the energy

in electron volts of a photon having a frequency of 100 MHz?

2 A photon with wavelength 0.1050 nm is incident on an electron

that is initially at rest If the photon scatters at an angle of 60.0o from its original direction, what are the magnitude and direction of the linear momentum of the electron just after the collision with the photon?

3 A 2.50-W beam of light of wavelength 124 nm falls on a metal surface You observe that the maximum kinetic energy of the

ejected electrons is 4.16 eV Assume that each photon in the beam ejects a photoelectron (a) What is the work function (in electron volts) of this metal? (b) How many photoelectrons are ejected each second from this metal? (c) If the power of the light beam, but not its wavelength, were reduced by half, what would be the answer to part (b)?

4 The star Betelgeuse has a surface temperature of 3000 K and is

600 times the diameter of our sun (If our sun were that large, we would be inside it!) Assume that it radiates like an ideal blackbody (a) If Betelgeuse were to radiate all of its energy at the

peak-intensity wavelength, how many photons per second would it

radiate? (b) Find the ratio of the power radiated by Betelgeuse to the power radiated by our sun (at 5800 K)

5 A harmonic oscillator consists of a 0.020-kg mass on a spring Its frequency is 1.50 Hz, and the mass has a speed of 0.36 m/s as it passes the equilibrium position (a) What is the value of the

quantum number n for its energy level? (b) What is the difference

in energy between the levels En and En+1? Is this difference

detectable?

6 For small amplitudes of oscillation the motion of a pendulum is

simple harmonic For a pendulum with a period of 0.500 s, find the ground-level energy and the energy difference between adjacent energy levels Express your results in joules and in electron volts Are these values detectable?

ĐÁP ÁN

CÂU 1

b) Wavelength of the photon:

Using the energy-wavelength relationship:

c) Frequency of the photon:

Using the energy-frequency relationship:

d) Energy in electron volts of a photon with a frequency of 100 MHz:

Convert the frequency to energy:

CÂU 2

Problem 2:

Given:

Wavelength of incident photon, λ=0.1050 nm

Scattering angle, θ=60.0∘

Find:

Magnitude and direction of the linear momentum

of the electron after the collision

Solution:

Initial momentum of the photon:

CÂU 3

roblem 4:

Given

Surface temperature of Betelgeuse, T=3000 K Diameter of Betelgeuse = 600 times the

diameter of the sun

a) Number of photons radiated per second at peak-intensity wavelength:

Peak wavelength using Wien's law:

CÂU 5