PPSC Physics Topic 7 Modern Physics With Answers

PPSC Physics Topic 7 Modern Physics

Sr. # Questions Answers Choice
1 The process of pair production will take place if the energy of photon is greater than. 0.21 MeV 0.51 MeV 1.51 MeV 1.21 MeV
2 For an electron or position the rest mass energy is equal to. 0.21 MeV 0.51 MeV 1.51 MeV 1.21 MeV
3 X-rays are absorbed maximum by Paper Copper Steel Lead
4 Why hydrogen atom does not emit x-rays. its size is very small It contains only single electron In it energy levels are for apart In it energy levels are close to each other
5 The possible values of principal quantum number are. only zero 0,1,2,...................7 1,2,3........................8 2,3,4,6...............10
6 In scattering experiment which force scatters alpha particle. Nuclear force Coulomb's force Gravitational force Centripetal force
7 During transition, atom cannot emit Visible light Ultraviolet radiation Infrared radiations gama rays
8 The radius of second orbit of hydrogen atom is 0.071 A 0.142 A 4.752 A 9.5298 A
9 The energy in an electromagnetic wave is carried in the units called. Protons Electrons Neutrons Nucleus
10 White light a tungsten filament lamp is passed through sodium vapor and viewed through a diffraction gritting Which of the following best describes the spectrum which would be seen. Coloured lines on a black background Coloured lines on a white background Dark lines on a coloured background Dark lines on a white background
11 The unit of Rydberg constant R is m m3 m<sup>-1</sup> m-2
12 The process of conversation of a photon into an electron and a position is called. Pair annihilations Pair production Photoelectric effect Compton effect
13 The phenomenon of Compton's effect process that right has Wave nature Particle nature Dual nature Corpuscular nature
14 In Compton's effect the change in wavelength of a scattered photon is called. Angle of emergence Angle of refraction Angle of deviation Compton shift
15 The angle of scattering for which the Compton shift is maximum is. 0<sup> o</sup> 45 <sup>o</sup> 80 o 180<sup> o</sup>
16 The phenomenon in which a photon of frequency 'f' is scattered by an electron and the scattered photon has frequency f <f is known as. Pair production Pair annihilations Photoelectric effect Compton's effect
17 In Compton's effect it was considered that X-rays consist of Electrons Holes Neutrons Protons
18 The phenomenon is which the wavelength of scattered X-rays is larger than the incident X-rays is known as. Zeeman's effect Photoelectric effect Compton's effect Annihilation of matter
19 Which one of the following spectra series is in the ultraviolet region. Lyman series Paschen series Brackett series Plund series
20 Which given element has lowest work function Na Al si C
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