 # Section 1 Question 1. If the photoelectric effect is observed for...

## Question

Section 1
Question 1.
If the photoelectric effect is observed for one metal, can you conclude that the effect will also be observed for another metal under the same conditions?
Explain.

Question 2.
If matter has a wave nature, why is this wave like characteristic not observable in our daily experiences?

Question 3.
The speed of light in water is 230 Mm/s.
Suppose an electron is moving through water at 250 Mm/s.
Does that violate the principle of relativity?

Question 4.
Give a physical argument that shows that it is impossible to accelerate an object of mass m to the speed of light, even with a continuous force acting on it.

Question 5.
Some distant astronomical objects, called quasars, are receding from us at half the speed of light (or greater).
What is the speed of light we receive from these quasars?

Section 2
Problem 1.
The average threshold of dark-adapted vision is 4.00 x 10-11 W/m2 at a central wavelength of 500 nm.
If light having this intensity and wavelength enters the eye and the pupil is open to its maximum diameter of 8.50 mm, how many photons per second enter the eye?

Problem 2.
An isolated copper sphere of radius 5.00 cm, initially uncharged, is illuminated by ultraviolet light of wavelength 200 nm.
What charge will the photoelectric effect induce on the sphere?
The work function for copper is 4.70 eV.

Problem 3.
(a) An electron has kinetic energy 3.00 eV.
Find its wavelength
(b) A photon has energy 3.00 eV.
Find its wavelength.

Problem 4.
An air rifle is used to shoot 1.00 gram particles at 100 m/s through a hole of diameter 2.00 mm.
How far from the rifle must an observer be to see the beam spread by 1.00 cm because of the uncertainty principle?
Compare answer with diameter of the visible universe (2 x 1026 m).

Problem 5.
A π mason is an unstable particle produced in high energy particle collisions.
Its rest energy is about 135 MeV, and it exists for an average lifetime of only 8.70 x 10-17 s before decaying into two gamma rays.
Using the uncertainty principle, estimate the fractional uncertainty Δm/m in its mass determination.

Problem 6.
An atomic clock moves at 1000 km/h for 1.00 hour as measured by an identical clock on the Earth.
How many nanoseconds slow will the moving clock be compared with the Earth Clock at the end of the 1.00 hour interval?

Problem 7.
A golf ball travels with a speed of 90.0 m/s.
By what fraction does its relativistic momentum magnitude p differ from its classical value mu?
i.e. find the ratio (p – mu)/mu

Problem 8.
A proton moves at 0.950c.
Calculate its (a) rest energy (b) total energy, and (c) kinetic energy.
Problem 9.
The rest energy of an electron is 0.511 MeV.
The rest energy of a proton is 938 MeV.
Assume that both particles have kinetic energies of 2.00 MeV.
Find the speed of (a) the electron and (b) the proton. (c) By hoe much does the speed of the electron exceed that of the proton?

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