Atoms and Nuclei · Physics · COMEDK

A hydrogen atom absorbs energy and rises to $n=3$ state from its ground state $n=1$. If the potential energy of the atom at its ground state is -13.6 eV , find the wave length emitted by it when it returns to its ground state:

{Planck's constant $=6.6 \times 10^{34} \mathrm{~J} \mathrm{~s}$ }

The main function of cadmium used in the nuclear reactor is:

What is the frequency of the electron in the first orbit of hydrogen atom of orbital radius $0.5 \times 10^{-10} \mathrm{~m}$, if its orbital velocity in that orbit is $2.2 \times 10^6 \mathrm{~ms}^{-1}$.

If the ratio of the nuclear radii of two atoms is $2: 3$ then the ratio of their mass numbers is:

The atomic mass of an element $10 X^{20}$ is 19.98170 amu. The binding energy per nucleon of that element is: [given mass of neutron = 1.00867amu and mass of proton = 1.00783 amu and 1amu = 931 MeV ]

An atom has a single electron. Its ground state energy is -30 eV and its first excited state energy is -8 eV . The atom is bombarded with a stream of photons, each of energy 15 eV .

Assuming the atom being in the ground state, which of the following statements is correct?

A. Atom gets excited to the first excited state and later emit photons of 22 eV

B. Atom absorbs energy continuously until 22 eV is accumulated and then gets excited

C. Atom will not get excited, and the transmitted light will have the same frequency as the incident light

D. Atom will absorb the photon and re-emit a photon of lower energy

A nucleus of uranium -235 absorbs a slow neutron and undergoes nuclear fission according to the reaction: ${ }_{92}^{235} U+{ }_0^1 n \rightarrow{ }_{56}^{141} B a+{ }_{36}^{92} K r+3{ }_0^1 n+Q$

If the average energy released per fission is 202 MeV , the energy released when 2.35 g of $U^{235}$ undergoes complete fission is approximately;

[Given $1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}$, Avogadro number $=6.02 \times 10^{23}$ ]

A mercury-198 nucleus is bombarded by a neutron, which causes a nuclear reaction

$$ n_0^1+\mathrm{Hg}_{80}^{198} \longrightarrow A u_{79}^{197}+X $$

What is the unknown product particle $X$ ?

Two deuterons are fused to form one alpha particle. If binding energy per nucleon of deuterium is 1.05 MeV and that of alpha particle is 7 MeV , what is the energy released in the formation of one alpha particle from the fusing of two deuterons?

An atom with one electron has ionization energy of 24 eV . An electron in this atom makes a transition from an excited energy level, where $\mathrm{E}=-15 \mathrm{eV}$, to the ground state. What is the wavelength of the emitted photon from this transition?

Which of the following is correct in the case of the Bohr model of atoms?

A. Predicts continuous emission spectra for all atoms

B. Assumes that the angular momentum of electrons is quantised

C. Predicts same emission spectrum for singly ionised neon atom and hydrogen atom

D. Predicts same emission spectrum for singly ionised neon atom and singly ionised helium atom

Which, of the following is true of the Balmer series of the hydrogen spectrum?

a. The series is in the visible region.

b. The entire series falls in the ultraviolet region

c. The entire series falls in the infrared region

d. The series is partly in the visible region and partly in the infrared region

The binding energy per nucleon for $$\mathrm{C}^{12}$$ is $$7.68 \mathrm{~MeV}$$ and that for $$\mathrm{C}^{13}$$ is $$7.47 \mathrm{~MeV}$$. The energy required to remove a neutron from $$\mathrm{C}^{13}$$ is

The distance of closest approach when an alpha particle of kinetic energy $$6.5 \mathrm{~MeV}$$ strikes a nucleus of atomic number 50 is

If an electron in a hydrogen atom jumps from the third orbit to the second orbit, it emits a photon of wavelength $$\lambda$$. When it jumps from the second to the first orbit, the corresponding wavelength of the photon will be

An electron has a mass of $$9.1 \times 10^{-31} \mathrm{~kg}$$. It revolves round the nucleus in a circular orbit of radius $$0.529 \times 10^{-10} \mathrm{~m}$$ at a speed of $$2.2 \times 10^6 \mathrm{~ms}^{-1}$$. The magnitude of its angular momentum is

$$ \text { If the nuclear radius of }{ }^{27} \mathrm{Al} \text { is } 3.6 \text { fermi, the nuclear radius of }{ }^{125} \mathrm{Fe} \text { is } $$

A nucleus with mass number 190 initially at rest emits an alpha particle. If the $$\mathrm{Q}$$ value of the reaction is $$4.5 \mathrm{~MeV}$$, the kinetic energy of the alpha particle is

In a hydrogen atom, if electron is replaced by a particle which is 40 times heavier but has the same charge, then, the ratio of the radius of the first excited state of a normal hydrogen atom to the ground state of the above atom is

The shortest wavelengths of Paschen, Lymen and Balmer series are in the ratio

The radius of a nucleus as measured by electron scattering is $$4.8 \mathrm{~fm}$$. The mass number of nucleus is most likely to be

The ratio of the radii of the nucleus of two element $$\mathrm{X}$$ and $$\mathrm{Y}$$ having the mass numbers 232 and 29 is:

The closest approach of an alpha particle when it make a head on collision with a gold nucleus is $$10 \times 10^{-14} \mathrm{~m}$$, then the kinetic energy of the alpha particle is :

Find the binding energy of the tritium nucleus: [Given: mass of $$1 \mathrm{H}^3=3.01605 \mathrm{~u} ; \mathrm{~m}_{\mathrm{p}}=1.00782 \mathrm{~u} ; \mathrm{~m}_{\mathrm{n}}=1.00866 \mathrm{~u}$$.]

The mass density of a nucleus varies with mass number $$A$$ as

The wavelength of the first line of Lyman series for $$\mathrm{H}$$ - atom is equal to that of the second line of Balmer series for a $$\mathrm{H}$$-like ion. The atomic number $$\mathrm{Z}$$ of $$\mathrm{H}$$-like ion is

The first emission of hydrogen atomic spectrum in Lyman series appears at a wavelength of

The mass number of two nuclei $$\mathrm{P}$$ and $$\mathrm{Q}$$ are 27 and 125 respectively. The ratio of their radii $$R_P: R_Q$$ is given by:

In a nuclear reaction 2 deuteron nuclei combine to form a helium nucleus. The energy released in $$\mathrm{MeV}$$ will be: (Given mass of deuteron $$=2.01355 \mathrm{~amu}$$. and mass of helium nucleus $$=4.0028 \mathrm{~amu}$$.

A particle at rest decays in to two particles of mass $$m_1$$ and $$m_2$$ and move with velocities $$v_1$$ and $$v_2$$. The ratio of their de Broglie wave length $$\frac{\lambda_1}{\lambda_2}$$ is:

The ground state energy of hydrogen atom is $$-13.6 \mathrm{~eV}$$. If the electron jumps from the $$3^{\text {rd }}$$ excited state to the ground state then the energy of the radiation emitted will be:

In the head-on collision of two alpha particles $$\alpha_1$$ and $$\alpha_2$$ with the gold nucleus, the closest approaches are 31.4 fermi and 94.2 fermi respectively. Then the ratio of the energy possessed by the alpha particles $$\alpha_2 / \alpha_1$$ is:

Which of the following statement is true when a gamma decay occurs from the nucleus of an atom?

During $$\alpha$$-decay, atomic mass of parent nuclei is

Which of the following series spectrum of hydrogen atom lies in ultraviolet region?

The wavelength of the second line of Balmer series is 486.4 nm. What is the wavelength of the first line of Lyman series?

The Lyman series of a hydrogen atom belongs in which category

If an electron in hydrogen atom jumps from an orbit of level $$n=3$$ to an orbit at level $$n=2$$, emitted radiation has a frequency of

(R = Rydberg's constant and c = velocity of light)

Ba-122 has half-life of 2 min. Experiment has to be done using Ba-122 and it takes 10 min to set up the experiment. It initially 80 g at Ba-122 was taken, how much Ba was left when experiment was started?

When the speed of light becomes $$\frac{2}{3}$$ of its present value, then the energy released in a given atomic explosion would

An electron of an atom transits from $$n_1$$ to $$n_2$$. In which of the following maximum frequency of photon will be emitted?

Two protons are kept at a separation of 40 $$\mathop A\limits^o $$. F$$_n$$ is the nuclear force and F$$_e$$ is the electrostatic force between them. Then,

Two radioactive materials X$$_1$$ and X$$_2$$ have decay constant 5$$\lambda$$ and $$\lambda$$, respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X$$_1$$ to X$$_2$$ will be $$1/e$$ after a time