Physi'cs 112 Exam 3 Spring 2006

41. Monochromatic light falls on two very narrow slits 0.048 rom apart. Successive fringes on a screen 5.00 m away are.6,S em apart near the center of the pattern. Vv'hat is the wavelength of the light?

p\ I(.y 620 urn Of ~ 0, Of g;)lP7 i'

'13. 580nm Y ':: ,S-.OOk/C. 540 nm D. 500 om )j ~ t. 5 eft7

E. 460 om -' .'~)

.. .,/.

A Total internal reflection B. Partial reflection from each surface

r9 Variation of index of refraction with wavelength 'D. Polariz..ation of light E. Selective absorption of different colors

43. Radio waves are readily diffracted around buildings whereas light waves are negligibly diffracted around buildings. This is becauseradio waves:

o Have much longer wavelengths than light waves B. Have much shorter wavelengths then light waves C. Are nearly monochromatic (single frequency) D. Are amplitude modulated E. Are plane polarized

44. In order to obtain a good single slit diffraction pattern, the slit width could be:

A. :VI 00 B. A/lO

XA. (8)10)·

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..... 45. Monochromatic light from a distant source is incident on a slit 0.75 mm wide. On a

screen 2.00 m away, the distance from the central maximum of the diffraction pattern to the first minimum is measured to be 1.35 mrn. Calculate the wavelength of the light.

253 om J =: J.15~tw@506mn X ':: f1, O()M C. 555 nm D. J:= 1.3S"Mm709 run E. 1012 nm .'/ .- ?

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42. The separation of white light into colors by a prism is associated with:

'I:;;:: O. 7S'/f)- 3,....\

A !2M

Physics 112 Exam 3 . Spring 2006

46. White light, with uniform. intensity across the visible range of 400 to 700 run, is perpendicularly incident on a water film, of index of refraction n= 1.33 and thickness t=320nm, that is suspended in air. At \",-hat wavelength is the light reflected by the film brightest to an observer? It. ~ " /.. ,/,,/7rtl 'ff II'

UE \' -,,-:-J--_----'/WJ~++.l.J,,~);;:-~:-~: I';;~ ~7hi J ]) 512run O/.-Z: ("'",. /1 /1'-1 J'..

"E. 567nm I Jllo:::' !l.i/? lor //l.=- / ;

J??+~ ),:0 ~~2/)""" 1.33 "56'1;,,,,J /+4.

47. Three polarizing sheets are placed in a stack with polarizing directions of the first and third perpendicular to each other. What angle should the polarizing direction of the middle sheet make with polarizing direction of the first sheet to obtain zero transmitted intensity when unpolarized light is incident on the stack?

00A B. 300

C. 45 0

D. 600

E. All angles allow light to pass through

48. What is the focal length of the eye-lens system when viev,ling an object at 33 cm from the eye? Assume that the lemH':etina distance is 2.0 cm.

A. 0.5 em I B. 0.9 cm i

C~ 1.5 cm I D? 1.9 em I E. 2.5 crn

!

49. A magnifying glass with a focal length of 8.5 cm is used to read print placed at a distance 7.5 em. Calculate the angular magnification.

•

A. 2.3x Ia ::; 1S-8TYt I I-~--!--S:-C!!}-/' }(;:0­ S ".:'. .% 3.3 @ 3.3x iT: ...,) 41'1'/

C. 4.3x .-1 I ---" Q~ - ------,D. 5.3x J 1)1 :: 4-{.3.KE. 6.3x I

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Physics 112 Exam3 Spring 2006

50. What is the magnifying power of an astronomical telescope using a refracting mirror whose radius of curvature is 6.0 m and an eyepiece whose focal length is 3.2 cm?

A. -25x ~ -:: 6. Om A -46x

(f;J -94x Ie ::3.jtfltD. -124x E. -154x

3. IJ.­ - -Yf'

51. Estimate the peak wavelength for radiation from the universe at 2.725 K, assuming black-body radiation?

A. 2.16x10· J5 m B. 3.02x10- 14 m

8C. 2.56x10' m D. 4.18x10·5 m

@ 1.06xIO·3 m

52. The work function for a certain sample is 2.3 eV. \Vhat is the stopping potential for electrons ejected from the sample by 7.0xl 014 Hz electromagnetic radiation?

53. Find the wavelength of the photon emitted by the hydrogen atom in the transltlOn from the fIrst exited level of to the ground level.

A. 1450 nrn• ..L­

B. 985 nm C. 550 om A D. 364 nrn /i1=/C9 122 nrn /l_fl

A. 0.1 V 100.6 VC., C. 0.9 V D. 1.5 V E. 9.0 V

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Page 4 of8

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Physics 112 Exam 3 Spring 2006

54. Franck and Hertz studied the motion of electrons through mercury vapor under the action of an electric field. When the electron kinetic energy was 4.geV or grater, the vapor emitt~avi01ethg Wh~t was the :vave length of tillS li~hq

A. l~:O'nm ..:-F,,-'::::_r.-:-,_l'_~1 £~) ~ A7fI ::~ !/._~_=:;....,6_.....-.~/7B. ZOO run (C) 250mn It-? 15. 300 nm I) fj .!l,n'" -,

E. 350run :: ;lS ItI")m/r.ql1~ -

55. Which of the following electromagnetic radiations has photons with greatest energy?

A. Blue light B. Yellow light

tUX-rays'1:5.' Radio waves

E. Microvaves

56. Determine the wavelength of difference of 100 V. . A A. 0.96 run B. 0.48 run <; 0.24 runaY 0.12 run E. 0.06 run

v= //?t!v I(p Ii ~ p;;--:."7/ @ £ ~ eV=

?~ (in7eV­~ -Jb .M) 71 //1-1"1 IJ /' L"? ":Jf+.2~

~ ::;(t.t-?·//l- J: i- ./1·1(}-~V·/.6·/v c-JI) V = D.D·;;' jP_A h 1. .II·!.' 111_ -IP

57. \\l11'1t is tile uncertainty in position, imposed by the uncertainty principle, on 150-g '.:/. .2. ./1) J,

baseball thrown at (93 ± 2) mph = (42 ± 1) m/s')"

/17 ;; /50

j.V:: Jmts -J,X-?,

!2:!-~n/1

- A. IxlO-3 m B. 2xlO-6 m C. 3xlO-14 m D. 4x10-24 m

(97Xlo-34 m

Page50f8

---

Physics 112 Exam 3 Spring 2006

58. An electron remains in an excited state of an atom for typically 10.8 s. What is the minimum uncertainty in the energy of the state?

@0.7x10·7 eV B. 0.6xl0-6 eV C. 0.5xl0·5 eV D. O.4xlO--4 eV E. 0.3xl0·3 eV

EAt ';r- t

4c;..~ u-l I!.--- ­

~.IY t/~

/~-

IA £; ;.,

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59. What is the energy difference. between the first excited state and the ground state of

an electron in th~ "box" of size L=lnm? / ,17 2 j 2 /

A. 9.8 eV ! /.:::: /I1IJo-I r / ;: 0 12 /B. 6.3 e~ Ol- pJ1 C"" 2.5 eV r- c: -? (- '2 )

@l.leV 1J£~·,e;.2-",:1 .. J - _ (r-/)) E. 0.5 eV 1/:-::.£ -c/ - .$L ?/71 I

~ -.Jf .. ) z i_--- --­oS • ~.b!J'JI) J:SI T _. ({.b3) 2. 'j/ -68 N81- '"'~

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60. For n = 4, what values can I have? ~\ ~ ! g./tJ -13J \

A. 0,1,2 I

(j) 0,1,2,3 C. 0, 1,2,3,4 ! D. -2,-1,0,1,2 E. -3, -2, -1, 0, 1,2,3

J

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Page 60f8

Physics 112 Exam 3 Spring 2006

Answer key

41 51

A 620 nm E L06xlO-3 m

42 e Variation of index of refraction with wavelength

43

52

B 0.6 V

53

A Have much longer wavelengths than light waves

44

E 122 nrn

54

D

45

10,. e 250nm

55 -

B 506nm

46

C

56

X-rays

E 567nm D 0.12 nm

47 57

A 00

48

E 1xlO-34 m

58

D 1.9 em

49 ....

A

59

0.7xIO·7 eV i I

B 3.3x

50

D 1.1 eV

60

e -94x B 0, 1,2,3

Page 80fl