PUNJAB PUBLIC SERVICE COMMISSION
COMBINED COMPETITIVE EXAMINATION
FOR RECRUITMENT TO THE POSTS OF PROVINCIAL MANAGEMENT SERVICE-2020
SUBJECT: PHYSICS (PAPER-II)
TIME ALLOWED: THREE HOURS MAXIMUM MARKS: 100
NOTE:I. All the parts (if any) of each Question must be attempted at one place instead of at different places
II. Write Q. No. in the Answer Book in accordance with Q. No. in the Q. Paper.
III. No Page/Space be left blank between the answers. All the blank pages of Answer Book must be crossed.
IV. Extra attempt of any question or any part of the question will not be considered.
Attempt FIVE Questions in all. Attempt in Urdu or English.
Attempt Five Questions in All, Selecting ONE from Section-1 and TWO each from Section-II and Section-III, Calculator is allowed (Not programmable). Attempt in Urdu or English.
SECTION-I
Q No.1: a) Distinguish between photoelectric effect and Compton effect. Also show that the Compton shift depends only on the scattering angle and not on the initial wavelength.
(b) The threshold frequency for photoelectric emission in copper is 1.1x15sec3, Find the maximum energy of the photoelectrons (in joules and electron volts) when light of frequency 1.5×15 sec is directed on a copper surface. (12+8=20 Marks)
Q No.2: (a) State Uncertainty principle. Describe its different forms,
(b) Derive time dependent Schrodinger wave equation in one dimension. (12+8=20 Marks)
SECTION-II
Q No.3: a) What is rectification? How diodes act as rectifier? Explain half and full wave rectifications in detail, support your answer by drawing circuits.
(b) Define NOR gate Describe its symbol, Boolean expression, truth table and circuit diagram. (14+6=20 Marks)
Q No.4: (a) What is transistor phase shift oscillator? Explain its circuit and operation in detail.
(b) What is common-emitter configuration of a transistor? Explain in detail. (12+8=20 Marks)
Q No.5: a) State radioactive decay law.
(b) Define half life of a radioactive element and determine an expression for the half life relating to decay constant
(c) Radioactive isotope of mercury 197Hg decays into 197gold Au with a decay constant of 0.016 (5) Calculate its life. (b) What fraction of this original amount will remain after three half lives. (4+8+8=20 Marks)
SECTION-III
Q No.6: a) What is mass spectrograph? Describe its principle, construction and working.
In a mass spectrometer, a singly charged positive ion(q-1.602 X 10(-20) emu) is accelerated through a potential difference of 1000 volts. It then travels through a uniform magnetic field for which H=1000 gauss, and is deflected into a circular path18.2 cm in radius. What is (a) the speed of the ion? (b) The mass of the ion, in grams and atomic mass units? (c) The mass number of the ion? (12+8=20 Marks)
No.7: (a) Prove that V.B = 0
(b) Write down the integral and differential form of Maxwell equations in the absence of magnetic or polarizable media.
(c) Differentiate between natural radioactivity and artificial radioactivity. (6+8+6=20 Marks)
Q No.8: (a) Define Ampere’s law. Derive the differential form of the Ampere’s law.
(b) State and prove Poynting theorem. (10+10=20 Marks)