## Advent of Modern Physics, Numerical Problems

See here solved numerical problems of Advent of Modern Physics, Chapter 8, Second Year Physics.

S .No Problem
Problem 1 The length of a spaceship is measured to be exactly one-third of its proper length. What is the speed of the spaceship relative to the observer?
See Solution
Problem 2 The time period of a pendulum is measured to be 3 s in the inertial frame of the pendulum. What is the period when measured by an observer moving with a speed of 0.95 c with respect to the pendulum?
See Solution
Problem 3 An electron which has a mass of 9.11 × 10-31 kg moves with a speed of 0.75 c. Find its relativistic momentum and compare this value with the momentum calculated from classical expression.
See Solution
Problem 4 An electron moves with a speed of v = 0.85 c. Find its total energy and K.E in electron volts.
See Solution
Problem 5 The rest mass of proton is 1.673 × 10-27 kg. At what speed would the mass go proton be tripled?
See Solution
Problem 6 At what fraction of speed of light must a particle move so that its K.E is one and a half times the rest energy
See Solution
Problem 7 A metal whose work function is 3.0 eV is illuminated by light of wavelength 3 × 10-7 m. Calculate (1) The threshold frequency (b) The maximum energy of photoelectron (c) The stopping potential.
See Solution
Problem 8 The thermal radiations from the sun peaks in the visible part of the spectrum. Estimate the temperature of the sun.
See Solution
Problem 9 A 50 keV X-rays is scattered through an angle of 900. What is the energy of the X-rays after Compton Effect?
See Solution
Problem 10 Calculate the wavelength of the de Broglie waves associated with electrons accelerated through a potential difference of 200 V.
See Solution
Problem 11 An electron is accelerated through a potential difference of 50 V. Calculate its de Broglie wavelength.
See Solution
Problem 12 The speed of an electron is measured to be 5 × 103 m/s to an accuracy of 0.003%. Find the uncertainty in determining the position of this electron.
See Solution
Problem 13 The life time of an electron is an excited state is about 10-8 s. What is its uncertainty in energy during this time?
See Solution