Physics Past Questions and Answers

Which of the following gives rise to the line spectra obtained from atoms?

A Kinetic energy of a moving atom
B Potential energy of an electron inside an atom
C Change of an electron from a higher to a lower energy level in the atom
D Disturbed proton in the nucleus
E Excitation of an electron in the atom

Question 292:

A stream of alpha particles is projected into an electric field between two plates X and Y as shown in the diagram above. Which of the following is correct? The particles are

A Accelerated and they continue in a straight line
B Directionally reversed at the end of the plates
C Deflected towards plate Y
D Attracted by both plates
E Deflected towards plate X.

Question 293:

An element whose half-life is 3 years has N atoms. How many atoms would have decayed after 9 years

A 1 N atoms8 Â Â Â Â Â Â Â Â Â Â Â Â Â
B 1 N atoms3
C 2 N atoms3 Â Â Â Â Â Â Â Â Â Â Â Â Â
D 5 N atoms6 Â Â Â Â Â Â Â Â Â Â Â Â Â
E 7 N atoms8 Â Â Â Â Â Â Â Â Â Â Â Â Â

Question 294:

When the nucleus of a uranium atom is split into two fragments of nearly equal mass the sum of the masses of the fragments is less than the mass of the original nucleus. This difference is a measure of the

A Experimental error in calculating the separate masses
B Change of momentum of each fragment
C Potential energy lost
D Nuclear energy released
E Kinetic energy lost

Question 295:

A sheet of paper is placed in the path of a beam of radiations from a radioactive source. Which of the following radiations will pass through the paper?I. Alpha rays II. Beta rays III. Gamma rays

A I only
B II only
C III only
D II and III only
E I, II and III