212 - Problem Set #13

Physics 212 Fall 2008 Problem Set #13 Read: 27.2, 28.1, 28.4 and then do the following. Due on Friday, November 21st. 1)

A certain metal has a work function of 2.28 eV. Calculate the maximum wavelength (in nm) that an electromagnetic wave can have in order for electrons to ONLY eject from the metal.

2)Ultraviolet light that has a frequency of 3 x 10

Hz in incident on a metal surface. The electrons that are ejected have a maximum kinetic energy of 6.1 eV. Calculate the work function of the metal in units of electron volts.

3)

4)

6)

A ball of mass 0.2 kg is released from rest at the top of a building that is 50 m tall. Calculate the de Broglie wavelength of the ball right before it hits the ground.

7)

A beam of electrons is incident on a single slit of width 0.5 nm that is 20 cm from a screen. A diffraction pattern is formed on the screen that has minima that are spaced 2.1 cm apart. What is the kinetic energy of the incident electrons?

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White light has wavelengths that range from 380 nm to 750 nm. This light in strikes a metal that has a work function of 2.28 eV. (a) What is the maximum kinetic energy (in joules) of the electrons that are emitted from the metal? (b) For what range of wavelengths will no electrons be emitted?

8)A proton is confined to a nucleus whose diameter is 5.5 x

EM waves of a certain wavelength cause electrons with a maximum kinetic energy of 0.68 eV to be ejected from a surface. The work function of the surface is 2.75 eV. The same EM waves are now incident on a different surface whose work function is 2.17 eV. What will be the maximum kinetic energy (in eV) of the electrons ejected from this different surface?

9)

10-15 m. Consider this distance to be the uncertainty in the position of the proton. Calculate the minimum uncertainty in the proton’s momentum. A ball of mass 50 g is traveling at 30 m/s. The speed of the ball is measured to an accuracy of 0.1%. Calculate the minimum uncertainty in its position.

ANSWERS: 1) 545 nm

2)6.3 Ev 3)a)1.6 x 10

5) 7.77 x 10-13 J 6) 1.06 X 10-34 m

J 7) 545 eV b) 545 nm - 750 nm 8) 1.9 x 10-20 kg m/s

5)A

proton in a particle accelerator has a de Broglie wavelength of 1.3 x 10-14 m. Calculate the kinetic energy (in joules) of the proton.

4)1.26 eV

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9) 7.0 x 10-32 m