Essential University Physics, 3e (Wolfson) 3e (Wolfson) Chapter 39 From Quarks to the Cosmos
3 9. 1 Co nc e pt ua lQue s t i o ns 1) Which of the following particles are leptons? (There may be more than one correct choice.) A) positron B) muon C) πmeson !) neutron ") electron Answer# A$ B$ " %ar# 1
&) 'articles that o not interact ia the strong force but o interact ia the wea* nuclear force (an presumably by the much wea*er graitation force) are calle A) baryons. B) mesons. C) harons. !) leptons. ") nucleons. Answer# ! %ar# 1
+) What type of particle is an electron? (There may be more than one correct co rrect choice.) A) lepton B) meson C) baryon !) nucleon ") haron Answer# A %ar# 1
,) What type of particle is a proton? (There may be more than one correct co rrect choice.) A) lepton B) meson C) baryon !) nucleon ") haron Answer# C$ !$ " %ar# 1
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) What type of particle is a neutron? (There may be more than one correct choice.) A) lepton B) meson C) baryon !) nucleon ") haron Answer# C$ !$ " %ar# 1
/) 2arons are iie into two subgroups calle A) baryons an leptons. B) leptons an mesons. C) mesons an baryons. !) nucleons an leptons. ") mesons an leptons. Answer# C %ar# 1
3) 2ow many ifferent *ins of leptons are *nown to e4ist$ incluing antiparticles as ifferent *ins? A) , B) / C) 5 !) & ") 1& Answer# " %ar# 1
5) Consier the possibility that a neutron coul eca y into a proton an a pion. What$ if any$ of the following conseration laws woul this process iolate? A) conseration of energy B) conseration of lepton number C) conseration of charge !) conseration of baryon number ") 6one of the aboe laws woul be iolate. Answer# A %ar# 1
7) Consier the ecay πo 8 9 : e:. This ecay is A) allowe. B) forbien because conseration of energy is iolate. C) forbien because conseration of baryon number is iolate. !) forbien because conseration of mass is iolate. ") forbien because conseration of lepton numbers is iolate. Answer# " %ar# 1
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1) Consier the ecay π: 8 9: : γ. This ecay is A) allowe. B) forbien because conseration of energy is iolate. C) forbien because conseration of baryon number is iolate. !) forbien because conseration of mass is iolate. ") forbien because conseration of lepton numbers is iolate. Answer# " %ar# 1
11) The reaction p : e 8 : e: is not possible because A) baryon number is not consere. B) lepton number is not consere. C) charge is not consere. !) energy is not consere. ") This reaction 0; possible. Answer# A %ar# 1
1&) The reaction p : 8 e: : γ is not possible because A) baryon number is not consere. B) lepton number is not consere. C) charge is not consere. !) energy is not consere. ") This reaction 0; possible. Answer# B %ar# 1
1+) The ecay n 8 p: : e : γ oes not occur because it woul iolate conseration of A) baryon number. B) lepton number. C) charge. !) energy. Answer# B %ar# 1
1,) What is the
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1) Composite particles that are compose of a
1/) Composite particles that are compose of three
13) Which of the following particles are mae up of
15) Which of the following particles is 6=T mae up of
17) >ien that the reaction n : π: 8 p can occur an that the
&) The cosmic bac*groun raiation correspons to a temperature of about A) 1., . B) &.3 . C) +.5 . !) ,.7 . ") . . Answer# B %ar# 1
3 9 . 2 Pr o bl e ms 1) ;uppose you were to try to create a protonantiproton pair by annihilation of two ery high energy gamma rays of the same waelength heaing towar each other. The proton an the anti proton hae the same masses$ but opposite charges. What woul be the minimum energy neee for each photon? (e @ 1./ 117 C$ m proton @ 1./3 1&3 *g$ c @ +. 15 ms) A) 1.&& e% B) 1&.& e% C) 155 e% !) 7+7 e% ") &&+ e% Answer# ! %ar# 1
&) A neutral D (haing mass ./,& u) that is at rest ecays into two gamma ray photons. What is the energy in e% of each photon? (1 u @ 7+1. e%c&) A) &77 e% B) 73 e% C) 117 e% !) 177 e% ") 1,7 e% Answer# A %ar# 1
+) 0s the ecay E: 8 p : π: allowe? A) Fes$ because it conseres energy. B) 6o$ because charge is not consere. C) 6o$ because mass is create. !) 6o$ because lepton number is not consere. Answer# B %ar# 1
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,) 0s the ecay π 8 9: : 9 allowe? A) Fes$ because it conseres energy. B) 6o$ because charge is not consere. C) 6o$ because mass is create. !) 6o$ because lepton number is not consere. Answer# B %ar# 1
) Which one of the following ecays CA6 o ccur? A) π: 8 9: : 9 B) p : n 8 p : p : C) : 8 π !) 9 8 e : e : 9 ") : 8 &π Answer# A %ar# 1
/) Which one of the following processes CA66=T occur? A) π: 8 9: : 9 B) π 8 &G C) π: : p 8 : : E: !) π : p 8 n + G ") E 8 π : p Answer# " %ar# 1
3) 2ow many
5) Consier the negatie pion$ π. (a) What combination of up an own
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7) 0f a gala4y is receing from us at .1c. Hse 2ubbleIs law to estimate the istance to this gala4y if the 2ubble constant is && *ms per million lightyears. (c @ +. 15 ms$ 1 ly @ 7.,/1 11 m$ 1 y @ +.1/ 13 s) A) 1., 17 ly B) /./ 1 ly C) /./ 1 ly !) &.& ly ") 1., 13 ly Answer# A %ar# 1
1) 0f the 2ubble constant is & *ms per million lightyears$ use it to estimate the age of the unierse? (c @ +. 15 ms$ 1 ly @ 7.,/1 11 m$ 1 y @ +.1/ 13 s) A) 1 >y B) 1& >y C) 1 >y !) & >y ") & >y Answer# B %ar# 1
11) 0f a gala4y is moing away from us at 1.J of the spee of light$ use 2ubbleIs law to estimate how far away it is from us if the 2ubble constant is && *ms per million lightyears. (c @ +. 15 ms$ 1 ly @ 7.,/1 11 m$ 1 y @ +.1/ 13 s) A) 1, ly B) 1, ly C) 1, thousan ly !) 1, million ly ") 1, billion ly Answer# ! %ar# 1
1&) "stimate the spee of a gala4y away from us if it is 1 billion lightyears from us an if the 2ubble constant is && *ms per million lightyears. (c @ +. 15 ms$ 1 ly @ 7.,/1 11 m$ 1 y @ +.1/ 13 s) A) .1c B) .+c C) .c !) .3c ") .7c Answer# ! %ar# 1
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1+) A giant star in another gala4y e4ploe /3 million years ago$ forming a supernoa. The eent is obsere by an astronomer on "arth. "stimate the spee at which the supernoa (an its gala4y) recees from "arth if the 2ubble con stant is && *ms per million lightyears. (c @ +. 15 ms$ 1 ly @ 7.,/1 11 m$ 1 y @ +.1/ 13 s) A) 1& *ms B) /3 *ms C) 1 *ms !) &3 *ms ") ,3 *ms Answer# C %ar# 1
1,) A gala4y is obsere receing from "arth with a spee of &5 *ms. 0f the 2ubble constant is && *ms per million lightyears$ estimate how many years ago the light that we presently see from the gala4y actually left the gala4y. (c @ +. 15 ms$ 1 ly @ 7.,/1 11 m$ 1 y @ +.1/ 13 s) A) 1.+ 15 y B) ,.& 15 y C) ,.& 13 y !) 1., 13 y ") ,.& 1/ y Answer# A %ar# 1
1) The bac*groun microwae raiation$ iscoere in 17/ by 'enKias an Wilson$ has its pea* intensity at a waelength of 1./ mm. What blac*boy temperature oes this waelength imply for the unierse? (L @ ./3 15 Wm& M ,$ Wien isplacement law constant is &.7 1+ m M ) A) &.3NC B) &3NC C) .&3 !) .NC ") &.3NC Answer# B %ar# 1
1/) ;uppose that the 2ubble constant ha the alue +. *ms per million lightyears. (1 y @ +.1/ 13 s$ m2 O m proton @ 1./3 1&3 *g$ c @ +. 15 ms$ 1 lightyear @ 7.,/1 1 1 m$ G @ /./3 111 6 M m&*g&) (a) What woul be the ma4imum ensity the unierse co ul hae that woul still allow it to e4pan foreer? (b) Hner the conitions of part (a)$ how many hyrogen atoms woul we e4pect to fin$ on the aerage$ in a olume of space measuring +. m by 5. m by 5. m? Answer# (a) &., 1&/ *gm+ (b) &5& atoms %ar# 1
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