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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 11901. |
When radiation of wavelength \[\lambda \] is incident on a metallic surface, the stopping potential is 4.8 volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping potential becomes 1.6 volts. Then the threshold wavelength for the surface is [EAMCET (Engg.) 2003] |
| A. | \[2\lambda \] |
| B. | \[4\lambda \] |
| C. | \[6\lambda \] |
| D. | \[8\lambda \] |
| Answer» C. \[6\lambda \] | |
| 11902. |
An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is [MP PMT 1993] |
| A. | \[5.9\times {{10}^{-4}}eV\] |
| B. | \[5.9\times {{10}^{-6}}eV\] |
| C. | \[5.9\times {{10}^{-8}}eV\] |
| D. | \[11.8\times {{10}^{-6}}eV\] \[(h=6.62\times {{10}^{-34}}Js;\ \ c=3\times {{10}^{8}}m/s)\] |
| Answer» C. \[5.9\times {{10}^{-8}}eV\] | |
| 11903. |
The kinetic energy of an electron is 5 eV. Calculate the de-Broglie wavelength associated with it (h = 6.6 ´ 10?34 Js, me = 9.1 ´ 10?31 kg) [Pb. PMT 2004] |
| A. | 5.47 Å |
| B. | 10.9 Å |
| C. | 2.7 Å |
| D. | None of these |
| Answer» B. 10.9 Å | |
| 11904. |
The de-Broglie wavelength \[\lambda \]associated with an electron having kinetic energy E is given by the expression [MP PMT 1990; CPMT 1996] |
| A. | \[\frac{h}{\sqrt{2mE}}\] |
| B. | \[\frac{2h}{mE}\] |
| C. | \[2mhE\] |
| D. | \[\frac{2\sqrt{2mE}}{h}\] |
| Answer» B. \[\frac{2h}{mE}\] | |
| 11905. |
Photon and electron are given same energy \[({{10}^{-20}}J)\]. Wavelength associated with photon and electron are \[{{\lambda }_{Ph}}\] and \[{{\lambda }_{el}}\] then correct statement will be [RPMT 2001] |
| A. | \[{{\lambda }_{Ph}}>{{\lambda }_{el}}\] |
| B. | \[{{\lambda }_{Ph}}<{{\lambda }_{el}}\] |
| C. | \[{{\lambda }_{Ph}}={{\lambda }_{el}}\] |
| D. | \[\frac{{{\lambda }_{el}}}{{{\lambda }_{Ph}}}=C\] |
| Answer» B. \[{{\lambda }_{Ph}}<{{\lambda }_{el}}\] | |
| 11906. |
The de-Broglie wavelength of a neutron at 27oC is l. What will be its wavelength at 927oC [DPMT 2002] |
| A. | l / 2 |
| B. | l / 3 |
| C. | l / 4 |
| D. | l / 9 |
| Answer» B. l / 3 | |
| 11907. |
The speed of an electron having a wavelength of \[{{10}^{-10}}m\] is [Manipal 1997; AIIMS 2002] |
| A. | \[7.25\times {{10}^{6}}\]m/s |
| B. | \[6.26\times {{10}^{6}}m/s\] |
| C. | \[5.25\times {{10}^{6}}m/s\] |
| D. | \[4.24\times {{10}^{6}}m/s\] |
| Answer» B. \[6.26\times {{10}^{6}}m/s\] | |
| 11908. |
For the Bohr's first orbit of circumference \[2\pi r\], the de-Broglie wavelength of revolving electron will be [MP PMT 1987] |
| A. | \[2\pi r\] |
| B. | \[\pi r\] |
| C. | \[\frac{1}{2\pi r}\] |
| D. | \[\frac{1}{4\pi r}\] |
| Answer» B. \[\pi r\] | |
| 11909. |
Assertion : The de-Broglie wavelength of a molecule varies inversely as the square root of temperature. Reason : The root mean square velocity of the molecule depends on the temperature. [AIIMS 1997] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion. | |
| 11910. |
Assertion : The specific charge of positive rays is not constant. Reason : The mass of ions varies with speed. [AIIMS 1999] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| Answer» C. If assertion is true but reason is false. | |
| 11911. |
An electron is moving with constant velocity along \[x-\]axis. If a uniform electric field is applied along \[y-\]axis, then its path in the \[x-y\] plane will be [MP PMT 1999] |
| A. | A straight line |
| B. | A circle |
| C. | A parabola |
| D. | An ellipse |
| Answer» D. An ellipse | |
| 11912. |
200 MeV of energy may be obtained per fission of \[{{U}^{235}}\]. A reactor is generating 1000 kW of power. The rate of nuclear fission in the reactor is |
| A. | 1000 |
| B. | \[2\times {{10}^{8}}\] |
| C. | \[3.125\times {{10}^{16}}\] |
| D. | 931 |
| Answer» D. 931 | |
| 11913. |
\[{{M}_{n}}\] and \[{{M}_{p}}\] represent mass of neutron and proton respectively. If an element having atomic mass M has N-neutron and Z-proton, then the correct relation will be |
| A. | \[M<[N{{M}_{n}}+Z{{M}_{P}}]\] |
| B. | \[M>[N{{M}_{n}}+Z{{M}_{P}}]\] |
| C. | \[M=[N{{M}_{n}}+Z{{M}_{P}}]\] |
| D. | \[M=N[{{M}_{n}}+{{M}_{P}}]\] |
| Answer» B. \[M>[N{{M}_{n}}+Z{{M}_{P}}]\] | |
| 11914. |
Energy generation in stars is mainly due to |
| A. | Chemical reactions |
| B. | Fission of heavy nuclei |
| C. | Fusion of light nuclei |
| D. | Fusion of heavy nuclei |
| Answer» D. Fusion of heavy nuclei | |
| 11915. |
The example of nuclear fusion is |
| A. | Formation of Ba and Kr from U235 |
| B. | Formation of He from H |
| C. | Formation of Pu 235 from U 235 |
| D. | Formation of water from hydrogen and oxygen |
| Answer» C. Formation of Pu 235 from U 235 | |
| 11916. |
The principle of controlled chain reaction is used in |
| A. | Atomic energy reactor |
| B. | Atom bomb |
| C. | The core of sun |
| D. | Artificial radioactivity |
| Answer» B. Atom bomb | |
| 11917. |
In an atomic bomb, the energy is released due to |
| A. | Chain reaction of neutrons and \[_{92}{{U}^{235}}\] |
| B. | Chain reaction of neutrons and \[_{92}{{U}^{238}}\] |
| C. | Chain reaction of neutrons and \[_{92}{{P}^{240}}\] |
| D. | Chain reaction of neutrons and \[_{92}{{U}^{236}}\] |
| Answer» B. Chain reaction of neutrons and \[_{92}{{U}^{238}}\] | |
| 11918. |
One requires energy \[{{E}_{n}}\]to remove a nucleon from a nucleus and an energy \['{{E}_{e}}'\]to remove an electron from the orbit of an atom. Then |
| A. | \[{{E}_{n}}={{E}_{e}}\] |
| B. | \[{{E}_{n}}<{{E}_{e}}\] |
| C. | \[{{E}_{n}}>{{E}_{e}}\] |
| D. | \[{{E}_{n}}\ge {{E}_{e}}\] |
| Answer» D. \[{{E}_{n}}\ge {{E}_{e}}\] | |
| 11919. |
Size of nucleus is of the order of |
| A. | \[{{10}^{-10}}m\] |
| B. | \[{{10}^{-15}}m\] |
| C. | \[{{10}^{-12}}m\] |
| D. | \[{{10}^{-19}}m\] |
| Answer» C. \[{{10}^{-12}}m\] | |
| 11920. |
Consider two nuclei of the same radioactive nuclide. One of the nuclei was created in a supernova explosion 5 billion years ago. The other was created in a nuclear reactor 5 minutes ago. The probability of decay during the next time is |
| A. | Different for each nuclei |
| B. | Nuclei created in explosion decays first |
| C. | Nuclei created in the reactor decays first |
| D. | Independent of the time of creation |
| Answer» C. Nuclei created in the reactor decays first | |
| 11921. |
The half-life of a sample of a radioactive substance is 1 hour. If \[8\times {{10}^{10}}\] atoms are present at \[t=0\], then the number of atoms decayed in the duration \[t=2\] hour to \[t=4\] hour will be |
| A. | \[2\times {{10}^{10}}\] |
| B. | \[1.5\times {{10}^{10}}\] |
| C. | Zero |
| D. | Infinity |
| Answer» C. Zero | |
| 11922. |
Nucleus produced due to a-decay of the nucleus \[_{Z}{{X}^{A}}\] is |
| A. | \[_{Z+2}{{Y}^{A+4}}\] |
| B. | \[_{Z}{{Y}^{A}}\] |
| C. | \[_{Z-2}{{Y}^{A-4}}\] |
| D. | \[_{Z-4}{{Y}^{A-2}}\] |
| Answer» D. \[_{Z-4}{{Y}^{A-2}}\] | |
| 11923. |
99% of a radioactive element will decay between |
| A. | 6 and 7 half lives |
| B. | 7 and 8 half lives |
| C. | 8 and 9 half lives |
| D. | 9 half lives |
| Answer» B. 7 and 8 half lives | |
| 11924. |
In \[_{88}R{{a}^{226}}\]nucleus, there are |
| A. | 138 protons and 88 neutrons |
| B. | 138 neutrons and 88 protons |
| C. | 226 protons and 88 electrons |
| D. | 226 neutrons and 138 electrons |
| Answer» C. 226 protons and 88 electrons | |
| 11925. |
The masses of neutron and proton are 1.0087 a.m.u. and 1.0073 a.m.u. respectively. If the neutrons and protons combine to form a helium nucleus (alpha particles) of mass 4.0015 a.m.u. The binding energy of the helium nucleus will be (1 a.m.u.= 931MeV) |
| A. | 28.4 MeV |
| B. | 20.8 MeV |
| C. | 27.3 MeV |
| D. | 14.2 MeV |
| Answer» B. 20.8 MeV | |
| 11926. |
The particles which can be added to the nucleus of an atom without changing its chemical properties are called |
| A. | Electrons |
| B. | Protons |
| C. | Neutrons |
| D. | None of the above |
| Answer» D. None of the above | |
| 11927. |
Decay constant of radium is\[\lambda \]. By a suitable process its compound radium bromide is obtained. The decay constant of radium bromide will be |
| A. | \[\lambda \] |
| B. | More than \[\lambda \] |
| C. | Less than \[\lambda \] |
| D. | Zero |
| Answer» B. More than \[\lambda \] | |
| 11928. |
Unit of radioactivity is Rutherford. Its value is |
| A. | \[3.7\times {{10}^{10}}\]disi tegrations/sec |
| B. | \[3.7\times {{10}^{6}}\]disintegrations/sec |
| C. | \[1.0\times {{10}^{10}}\] disintegrations/sec |
| D. | \[1.0\times {{10}^{6}}\] disintegrations/sec |
| Answer» E. | |
| 11929. |
A sample contains 16 gm of a radioactive material, the half-life of which is two days. After 32 days, the amount of radioactive material left in the sample is |
| A. | Less than 1 mg |
| B. | \[\frac{1}{4}gm\] |
| C. | \[\frac{1}{2}gm\] |
| D. | 1 gm |
| Answer» B. \[\frac{1}{4}gm\] | |
| 11930. |
Some radioactive nucleus may emit |
| A. | Only one \[-13.6\ eV\] or \[\gamma \]at a time |
| B. | All the three \[_{92}{{U}^{238}}\] and \[\gamma \] one after another |
| C. | All the three \[\alpha ,\ \beta \] and \[\gamma \] simultaneously |
| D. | Only\[\alpha \] and \[\beta \] simultaneously |
| Answer» B. All the three \[_{92}{{U}^{238}}\] and \[\gamma \] one after another | |
| 11931. |
In the reaction \[_{1}^{2}H+_{1}^{3}H\to _{2}^{4}He+_{0}^{1}n\]. If the tending energies of \[_{1}^{2}H,\text{ }_{1}^{3}H\text{ and }_{2}^{4}He\] are respectively \[a,\text{ b and }c\] (in MeV), then the energy (in MeV) released in this reaction is |
| A. | \[c+a-b\] |
| B. | \[c-a-b\] |
| C. | \[a+b+c\] |
| D. | \[a+b-c\] |
| Answer» C. \[a+b+c\] | |
| 11932. |
1 atomic mass unit is equal to |
| A. | \[\frac{1}{25}\] (mass of \[{{F}_{2}}\] molecules) |
| B. | \[\frac{1}{14}\] (mass of \[{{N}_{2}}\] molecules) |
| C. | \[\frac{1}{12}\] (mass of one C-atom) |
| D. | \[\frac{1}{16}\] (mass of \[{{O}_{2}}\] molecules) |
| Answer» D. \[\frac{1}{16}\] (mass of \[{{O}_{2}}\] molecules) | |
| 11933. |
A \[^{7}Li\] target is bombarded with a proton beam current of \[{{10}^{-4}}\] A for 1 hour to produce \[^{7}Be\] of activity \[1.8\times {{10}^{8}}\] disintegrations per second. Assuming that one \[^{7}Be\] radioactive nucleus is produced by bombarding 1000 protons, determine its half-life. |
| A. | \[8.6\times {{10}^{6}}s\] |
| B. | \[4.2\times {{10}^{5}}s\] |
| C. | \[3.1\times {{10}^{5}}s\] |
| D. | \[1.1\times {{10}^{6}}s\] |
| Answer» B. \[4.2\times {{10}^{5}}s\] | |
| 11934. |
Radium \[^{226}Ra,\] spontaneously decays to radon with the emission of an \[\alpha -\]particle and a \[\gamma \] ray. If the speed of the \[\alpha \] particle upon emission from an initially stationary radium nucleus is \[1.5\times {{10}^{7}}m/s,\] what is the recoil speed of the resultant radon nucleus? Assume the momentum of \[\gamma \]ray is negligible compared to that of \[\alpha \]particle. |
| A. | \[1.6\times {{10}^{4}}m/s\] |
| B. | \[2.7\times {{10}^{5}}m/s\] |
| C. | \[1.3\times {{10}^{6}}m/s\] |
| D. | \[2.6\times {{10}^{3}}m/s\] |
| Answer» C. \[1.3\times {{10}^{6}}m/s\] | |
| 11935. |
When a \[{{U}^{238}}\] nucleus originally at rest, decays by emitting an alpha particle having a speed the recoil speed of the residual nucleus is |
| A. | \[\frac{4u}{238}\] |
| B. | \[-\frac{5u}{234}\] |
| C. | \[\frac{4u}{234}\] |
| D. | \[-\frac{4u}{238}\] |
| Answer» D. \[-\frac{4u}{238}\] | |
| 11936. |
In a sample of rock, the ratio of \[^{206}Pb\] to \[^{238}U\] nuclei is found to be 0.5. The age in year of the rock is (given half-life of \[\,{{U}^{238}}\] is \[4.5\times {{10}^{9}}\] years) |
| A. | \[2.25\times {{10}^{9}}\] |
| B. | \[4.5\times {{10}^{9}}l\,\,n3\] |
| C. | \[4.5\times {{10}^{9}}\frac{ln\left( \frac{3}{2} \right)}{ln2}\] |
| D. | \[2.25\times {{10}^{9}}ln\left( \frac{3}{2} \right)\] |
| Answer» D. \[2.25\times {{10}^{9}}ln\left( \frac{3}{2} \right)\] | |
| 11937. |
Two radioactive substances A and B have decay constants \[5\lambda \] and \[\lambda \] respectively. At t=0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be \[{{(1/e)}^{2}}\] after a time interval |
| A. | \[4\lambda \] |
| B. | \[2\lambda \] |
| C. | \[1/2\lambda \] |
| D. | \[1/4\lambda \] |
| Answer» D. \[1/4\lambda \] | |
| 11938. |
Two radioactive materials \[{{X}_{1}}\] and \[{{X}_{2}}\] have decay constants \[10\lambda \] and \[\lambda \] respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of \[{{X}_{1}}\] to that of \[{{X}_{2}}\] will be 1/e after a time |
| A. | \[\frac{1}{10\lambda }\] |
| B. | \[\frac{1}{11\lambda }\] |
| C. | \[\frac{11}{10\lambda }\] |
| D. | \[\frac{1}{9\lambda }\] |
| Answer» E. | |
| 11939. |
Consider \[\alpha \] particles, \[\beta \] particles and \[\gamma \] - rays, each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are: |
| A. | \[\alpha ,\,\,\beta ,\,\,\gamma \] |
| B. | \[\alpha ,\,\,\beta ,\,\,\gamma \] |
| C. | \[\beta ,\,\,\gamma ,\,\,\alpha \] |
| D. | \[\gamma ,\,\,\beta ,\,\,\alpha \] |
| Answer» B. \[\alpha ,\,\,\beta ,\,\,\gamma \] | |
| 11940. |
A radioactive element X converts into another stable element Y. Half-life of X is 2 hrs. Initially only X is present. After time t, the ratio of atoms of X and Y is found to be 1 : 4, then t in hours is |
| A. | 2 |
| B. | 4 |
| C. | between 4 and 6 |
| D. | 6 |
| Answer» D. 6 | |
| 11941. |
` Half lives of two isotopes X and Y of a material are known to be \[2\times {{10}^{9}}years\] and \[4\times {{10}^{9}}years\,\]respectively If a planet was formed with equal number of these isotopes, then the current age of planet, given that currently the material has 20% of X and 80% of Y by number, will be |
| A. | \[2\times {{10}^{9}}years\] |
| B. | \[4\times {{10}^{9}}years\,\] |
| C. | \[6\times {{10}^{9}}years\] |
| D. | \[8\times {{10}^{9}}years\] |
| Answer» E. | |
| 11942. |
An archaeologist analyses the wood in a prehistoric structure and finds that \[{{C}^{14}}\] (Half-life = 5700 years) to \[{{C}^{12}}\]is only one-fourth of that found in the cells of buried plants. The age of the wood is about |
| A. | 5700 years |
| B. | 2850 years |
| C. | 11,400 years |
| D. | 22,800 years |
| Answer» D. 22,800 years | |
| 11943. |
Two radioactive materials A and B have decay constant \[\frac{13}{7}\] units and \[\frac{19}{14}\] units respectively. Directly both have the same number of nuclei. The time (in same system of units), after which the ratio of their remaining nuclei will be 1/e is |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 5 |
| Answer» B. 3 | |
| 11944. |
Consider the following reaction \[_{1}{{H}^{2}}{{+}_{1}}{{H}^{2}}{{\to }_{2}}{{H}^{4}}+Q.\] If \[m\,{{(}_{1}}{{H}^{2}})=2.014\,\,lamu;\] \[m\,{{(}_{2}}{{H}^{4}})=4.0024\,\,lamu.\] The energy Q released (in MeV) in this fusion reaction is |
| A. | 12 |
| B. | 6 |
| C. | 24 |
| D. | 48 |
| Answer» D. 48 | |
| 11945. |
Imagine that a reactor converts all given mass into energy and that it operates at a power level of 109 watt. The mass of the fuel consumed per hour in the reactor will be : (velocity of light, c is \[3\times {{10}^{8}}m/s\]) |
| A. | \[0.96\text{ }gm\] |
| B. | \[0.8\text{ }gm\,\] |
| C. | \[4\times {{10}^{-2}}gm~~~~~\] |
| D. | \[6.6\times {{10}^{-5}}gm\] |
| Answer» D. \[6.6\times {{10}^{-5}}gm\] | |
| 11946. |
If a star can convert all the He nuclei completely into oxygen nuclei, the energy released per oxygen nuclei is [Mass of \[He\] nucleus is 4.0026 amu and mass of Oxygen nucleus is 15.9994 mu] |
| A. | 7.6 MeV |
| B. | 56.12 MeV |
| C. | 10.24 MeV |
| D. | 23.9 MeV |
| Answer» D. 23.9 MeV | |
| 11947. |
The nuclear fusion reaction\[2{{H}^{2}}{{\to }_{2}}H{{e}^{4}}+\text{Energy }\], is proposed to be used for the production of industrial power. Assuming the efficiency of process for production of power is 20%, find the ass of the deuterium required approximately for a duration of 1 year. Given mass of \[_{1}{{H}^{2}}\] nucleus = 2.0141 a.m.u and mass of\[_{2}H{{e}^{4}}\] nuclei = 4.0026 a.m.u and 1 a.m.u. = 31 MeV |
| A. | 165kg |
| B. | 138kg |
| C. | 180kg |
| D. | 60kg |
| Answer» C. 180kg | |
| 11948. |
A heavy nucleus having mass number 200 gets disintegrated into two small fragments of mass number 80 and 120. If binding energy per nucleon for parent atom is 6.5 MeV and for daughter nuclei is 7 MeV and 8 MeV respectively, then the energy released in the decay will be - |
| A. | 200 MeV |
| B. | -220 MeV |
| C. | 220 MeV |
| D. | 180 MeV |
| Answer» D. 180 MeV | |
| 11949. |
The nuclear radius of \[_{8}{{O}^{16}}\] is \[3\times {{10}^{-15}}\]. If an atomic mass unit is \[1.67\times {{10}^{-27}}kg\], then the nuclear density is approximately |
| A. | \[2.35\times {{10}^{17}}g/c{{m}^{-3}}\] |
| B. | \[2.35\times {{10}^{17}}kg/c{{m}^{-3}}\] |
| C. | \[2.35\times {{10}^{17}}c{{m}^{-3}}\] |
| D. | \[2.35\times {{10}^{17}}kg\,\,m{{m}^{-3}}\] |
| Answer» C. \[2.35\times {{10}^{17}}c{{m}^{-3}}\] | |
| 11950. |
The particles emitted by radioactive decay are deflected by magnetic field. The particles will be [RPET 1997] |
| A. | Protons and \[\alpha -\]particles |
| B. | Electrons, protons and \[\alpha -\]particles |
| C. | Electrons, protons and neutrons |
| D. | Electrons and \[\alpha -\]particles |
| Answer» E. | |