PPSC Physics Topic 7 Modern Physics With Answers

PPSC Physics Topic 7 Modern Physics

Sr. # Questions Answers Choice
1 The minimum amount of energy in an individual electron has to gain to escape from a particular surface is called. Threshold frequency work function Wave number Kinetic energy
2 The total energy of the hydrogen atom is zero Infinite positive Negative
3 Lines of Balmer series are emitted by hydrogen atom when the electron jumps from The first orbit to any other orbit Higher orbits to second orbit Higher orbits to first orbit The third orbit to higher orbit
4 What will be excitation energy in the third orbit of hydrogen atom. 0.66 eV 0.85 eV 1.5 eV 5.4 eV
5 Which of the following quantities is discrete according to Bohr's hypothesis. Momentum <div>Potential energy</div> Angular velocity Angular momentum
6 The Rutherford atom according to classical theory is Stable Unstable Partially stable Quantized
7 The mass defect of Bohr's atomic model is Exclusion of nuclear motion missing of classical and quantum theories Failed to explain the fine structure of spectral line All of the above
8 Which quantity remains fixed in isobars. Mass number Atomic number Number of neutrons Number of protons
9 Which given quantity remains the same in isotones. Mass number Atomic number Number of neutrons Number of protons
10 Photocells are used for Security systems Counting systems Automatic door system All of the above
11 In a photocell, certain metals emit electrons for Visible light X-rays Infrared light Ultraviolet light
12 In potential for the material of cathode pure metals are rarely used because of their Low reflecting power High reflecting power Low resolving power High resolving power
13 An increase in frequency above threshold frequency results in. Increase in photo electric current Increase in K.E. of electrons Decrease in photoelectric current Decreases in K.E. of electrons
14 In the experiment of photo electric effect the minimum frequency of photons at which electrons are emitted from a metal surface is called. Critical frequency Typical frequency Threshold frequency Surface frequency
15 The emission of electrons from a metal surface when exposed to light of suitable frequency is called. Pair production Compton effect Photo electric effect Zeeman effect
16 When light of particular frequency is allowed to fall upon a metal surface electrons are emitted from a these emitted electrons are called. Photons Holes Quants Photo electrons
17 The value of principal quantum number for an ionized atom is. 13.6 eV 27.2 eV 54.4 eV 100 eV
18 Isotopes are the atoms of the same elements which contain equal number of. Nucleus Neutrons Protons Electrons
19 The unit Planck's constant is equivalent to that of. Energy Force Velocity Angular momentum
20 Which of the following atom pair have the same structure. N, C B, Li H2 , Ne Li , Na
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