Physics Chapter 13 Entry test MCQs
76. Wavelength of Gamma-rays is:
a. Longer than X-rays
b. Equal to the X-rays
c. Broader than X-rays
d. Shorter than X-rays
77. Thorium is transformed after the emission of ẞ-particle into:
a. Protactinium
b. Bismuth
c. Palladium
d. Polonium
78. Emission of gamma-rays from radioactive element result into:
a. Decrease of mass number by 1
b. Increase of charge number 1
c. Decrease charge number by 1
d. No change in the charge number
79. The relation between decay constant λ and half-life ‘T1/2’ of radioactive substance is:
a. λ = 0.693 T1/2
b. λ = 1/ T1/2
c. λ = 0.693 /T1/2
d. λ = T1/2
80. Radiation damages living organism is primarily due to:
a. Photo electric effect
b. Excitation phenomena
c. Heating
d. Ionization
81. complete the Radioactive equation 
82. The quantity of uranium is 400g. After 3rd half-life, how much uranium will be left?
a. 25g
b. 50g
c. 200g
d. 100g
83. The half-life of radium is about 1600 years. If 100 g radium existing now, 25 g will remain un-decayed after:
a. 6400 years
b. 4800 years
c. 3200 years
d. 2400 years
84. Which of the following has maximum ionizing power?
a. ẞ
b. α
c. Neutron
d. γ
85. A radioactive Nucleus X undergoes a series of decay according to the same:
if the mass number and atomic number of X are 180 and 72 respectively, the corresponding number of x4 are:
a. 176,69
b. 172,69
c. 176,7
d. 172,71
86. Calculate the activity (decaying atom per unit time) of strontium-90 having 6.7 x 1021atoms at t= 0 decay constant of strontium 8.3 x 10-10 s-1
a. 5.6 x 1011 s-1
b. 8.01 x 1010Bq
c. 12 x 1011Bq
d. 5.6 x 1012 Bq
87. Calculate the half-life of bismuth-214 which has a decay constant of 4.3 x 103 s-1
a. 1.6 x 10-4 s
b. 2.9 x 10-4 s
c. 2.9 x 101 s
d. 3.9 x 101 s
88. Two radioactive samples, S1 and S2 have half-live 3 hours and 7 hours respectively. If they have the same activity at certain instant t, what is the ratio of the number of atoms of S1 to S2 at instant t?
a. 3:7
b. 9:49
c. 7:3
d. 49:9
89. In relation λ T1/2 = 0.693 which quantity is represented by λ.
a. Wavelength
b. Half-life
c. Decay constant
d. Activity
90. The main difference between X-Rays and y-Rays is:
a. Energy
b. Frequency
c. Origin
d. Wave length
91. There are initially 400 atoms in a radioactive sample. What would be the number of atoms after 3 half-lives?
a. 50
b. 400
c. 25
d. 200
92. While using radiation therapy, cancerous thyroid is treated with radioisotope:
a. Thorium
b. Carbon
c. Iodine-131
d. 235 uranium
93. Half-life of iodine-131 is 8 days. If 20mg is present initially, how much iodine is left behind after 2 half-lives?
a. 2.5 mg
b. 10 mg
c. 1.25 mg
d. 5 mg
94. 4.5 x 109 year is the half-life of:
a. U236
b. U238
c. U14
d. U235
95. Number of Quarks in hydrogen atom
a. 3
b. 1
c. 4
d. 2
96. Which radiations more ionization
a. Gamma
b. Alpha
c. Beta
d. None
97. High speed beta rays are
a. Electron and positron
b. Electron
c. Proton
d. Positron