2B SP ‘09

PHOTOELECTRIC EFFECT

9. ( 10 points) What is the energy  in Joules (J) of photons emitted by  radio station KQED FM, frequency f = 88.5 MHz?  Note: 1  MHz = 10 6 Hz and  h = 6.63x10 -34 J·s. 

10.  (15 points) The longest wavelength of light that will emit electrons from a certain metal is λ =  402 nm.

(a) (4 points) What is the frequency f of the light with that wavelength?
 
(b) (4 points) What is the metal’s work function Wo in Joules (J) ?
Note: h = 6.63x10 -34 J·s.  

 

(c ) (7 points) What would be the kinetic energy (in Joules) of an emitted electron if the incident light had wavelength λ = 201 nm?

ATOMIC LINE SPECTRA AND ENERGY LEVELS/BOHR MODEL

11.  (12 points)   For the two hydrogen transitions (i) and (ii) indicated below, n is the initial state and n’  is the final state.


(i) n = 1 and n’ = 3  (ii) n = 6 and = n’ = 2. 


As a reference,  you may recall that the hydrogen energy levels are given by  En = -13.6 eV/n2.

(a) (3 points) Which transition involves the largest energy photon,  (i) or (ii)?  Circle one.

(b ) (3 points) Which transition involves the largest frequency photon,  (i) or (ii)?  Circle one.

(c ) (3 points) Which transition involves the largest wavelength photon,  (i) or (ii)?  Circle one.


(d) (3 points) Which transition involves photon absorption,  (i) or (ii)?  Circle one.

4C FALL ‘98 PHOTOELECTRIC EFFECT

2. (20 points) Ch. 40 (OF THE OLD BOOK)
This problem deals with the photoelectric effect. The stopping potential for photoelectrons emitted from a surface illuminated by light of wavelength = 491 nm
is V1 = 0.710 V. When the incident wavelength is changed to a new value , the stopping potential is found to be V2 = 1.43 V.

(a) (10 points) What is the new wavelength ?

(b) (10 points) What is the work function of the metal

2B SP ‘99 ATOMIC LINE SPECTRA AND ENERGY LEVELS/BOHR MODEL

7.  ( 20  points)

 

(a)(10 points) If an electron makes a transition from the n = 3 Bohr orbit to the n =1 orbit in hydrogen, find the wavelength of the photon created in this process.

(b)(10 points) Assuming that the atom was initially at rest, find the recoil speed of the hydrogen atom when this photon is emitted. HINT: USE CONVERSATION OF MOMENTUM; IGNORE THE ELECTRON MASS

4C SP AU ‘01 PHOTOELECTRIC EFFECT

3.  (20  points) Summary problem from Ch. 38 (EQUIVALENT CHAPTER IN OLD BOOK)  and other relevant Chapters in volume 2 of your textbook FROM PHYSICS 4B:  Click here for a review of Physics 4B--SEE CH. 27. 
         Photons of wavelength 450 nm are incident on a metal. The most energetic electrons  are ejected from the metal with speed v. The electrons  enter with this speed v  into a region of magnetic field that points inward to the page; they are then bent into a circular arc of radius r = 0.20 m by this magnetic field of magnitude 2.0 x 10 - 5 T.  See the diagram of this situation below. What is the work function   of the metal ?

 

 

2B SP’11  PHOTOELECTRIC EFFECT

7. (12 points)    When a  beam  of UV (ultra violet)  radiation,  wave length  285 nm,  falls on a metal surface,   the maximum  kinetic energy of emitted electrons is KE = 5.20x10 – 19 J.  Note: h = 6.626x10 -34 J· s.

 What is the maximum kinetic energy KE’ ( in Joules) , when a beam of visible light,  wavelength 632. 8 nm,   falls on the same metal surface?

2B SP ’08  

PHOTOELECTRIC EFFECT

3.  (30 points)   Light is  shined on a metal surface.  As indicated below, electrons are ejected only if the incident light has  a frequency that is at least equal to 5.40 x 1014 Hz.
 
What is the maximum kinetic  energy of ejected electrons when the  frequency of the light is 6.70x10 14 Hz?   

 

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4 (20 points) ATOMIC LINE SPECTRA AND ENERGY LEVELS/BOHR MODEL:
Initially an electron is in the n = 2 state of hydrogen. Find the energy of  the photon  needed to excite the electron to the n = 4 state.

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5.  (20 points)  ATOMIC LINE SPECTRA AND ENERGY LEVELS/BOHR MODEL:
Initially an electron is in the n = 3 state of hydrogen. Suppose the electron absorbs a 1.2336-eV photon.
      What is the value of n in the final state of the electron ?

 

4C SP ‘02

PHOTOELECTRIC EFFECT

2. (a) (28 points) This problem deals with the photoelectric effect. The stopping potential for photoelectrons emitted from a surface illuminated by light of wavelength = 487 nm is V = 0.698 V. At what  incident wavelength is  the stopping potential equal to zero?

(b) (2 points) Circle the correct answer: Who invented the photoelectric effect?  (1) Bill Gates (2) Einstein   (3) Hertz  (4) Maxwell (5) Planck

4C SP ‘04

ATOMIC LINE SPECTRA AND ENERGY LEVELS/BOHR MODEL

5.   (22 points) A hydrogen atom, initially in the  ground state (ni = 1) absorbs a photon of wavelength 122.00 nm.
(a) (12) What is the final state ? (In other words,  solve for nf .) Show all work.

(b) (8) EXTRA CREDIT : What is the maximum value of ,  orbital angular momentum number , of the electron in the final state?

(c) (2) EXTRA CREDIT:  In units of , what is the largest possible value of Lz  corresponding to the  you found in part (b)?