Physics Past Questions and Answers

A radioactive substance has a half-life of 20 hours. What fraction of the original radioactive nuclei will remain after 80 hours?

A 1/32
B 1/16
C 1/8
D 1/4
E 1/2

Question 167:

A metal is illuminated with a radiation of energy 6.88eV If the kinetic energy of the emitted electrons is 1.5OeV, calculate the work function of the metal.

A 0.22eV
B 4.59eV
C 5.38eV
D 8.38eV
E 10.32eV

Question 168:

Viscosity in a liquid does not depend on the

A Nature of the liquid
B Relative velocity between the liquid layers
C Area of the surfaces in contact
D Temperature of the liquid
E Normal reaction between the liquid layers

Question 169:

Which of the following is not crystal?

A Sodium chloride
B Lead
C Copper (II) tetraoxosulphate (VI)
D Glass
E Germanium

Question 170:

What is the difference between a crystalline and an amorphous solid? A crystalline solid

A Has cubic structure while amorphous solid has hexagonal structure
B Has regularly-repeating pattern while an amorphous solid has not
C Is white while amorphous solid is yellow
D Is always hard while amorphous solid is always soft
E Melts on heating while an amorphous solid sublimates on heating.