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IGNOU BPHET-141 (January 2025 – December 2025) Assignment Questions

PART A

1. a) A spacecraft A has a speed 0.80c with respect to the Earth. If the speed of another spacecraft B with respect to spacecraft A is 0.50c, what is the speed of B with respect to the Earth

b) A particle is travelling through the Earth’s atmosphere at a speed of 0.6c. To an Earth-bound observer, the distance it travels is 4.0 km. How far does the particle travel in its own frame of reference?

c) A particle of rest mass 2.0 kg has an initial speed of 8 210 ms-1. A constant relativistic force of magnitude 6 1.5 10 N is exerted on the particle in the same direction as the initial relativistic momentum for 1000 s. Calculate the magnitudes of the initial and final relativistic linear momentum and its final speed.

d) A star emits light with wavelength 420 nm. An observer on earth measures the wavelength of the light received from the star to be 600 nm. Calculate the speed with which the star is moving.

2. a) Determine the wavelengths of the photons scattered at (i) 60 and (ii) 90 when Xrays of wavelength 4.5 pm are scattered from a target.

IGNOU BPHET-141 (January 2024 – December 2024) Assignment Questions

BPHET-141 Assignments Details

University	:	IGNOU (Indira Gandhi National Open University)
Title	:	Elements of Modern Physics
Language(s)	:	English, Hindi
Code	:	BPHET-141
Degree	:	BSCG
Subject	:	Physics
Course	:	Discipline Specific Electives (DSE)
Author	:	Gullybaba.com Panel
Publisher	:	Gullybaba Publishing House Pvt. Ltd.