Atoms and Nuclei

If an electron is moving in the 4th orbit of the hydrogen atom, then the angular momentum of the electron in SI unit is

If $F_1, F_2$ and $F_3$ are the relative strengths of the gravitational, the weak nuclear and the electromagnetic forces respectively, then

If $S$ is the surface area of a nucleus of mass number $A$, then

The energy equivalent to a mass of 1 kg is

In the following nuclear reaction $X$ is
\({ }_{13} \mathrm{Al}^{27}+{ }_2 \mathrm{He}^4 \longrightarrow{ }_0 n^1+X\)

If $F_1$ and $F_2$ are the relative strengths of the gravitational and weak nuclear forces respectively, then $F_2 / F_1$ is nearly

Nuclear fission and fusion can be explained on the basis of

The ratio of the energies of the electron in the hydrogen atom in the first and second excited states is

Which of the following statements is true?

Estimate the approximate volume of aluminium nucleus $(A=27)$, use $\binom{R_0 \simeq 1.0 \times 10^{-15} \mathrm{~m}}{\pi \simeq 3}$

The energy of an electron in the fourth excited state of the hydrogen atom is

Among the fundamental forces, which one of the following is the strongest force?

What will be the energy released in joule, in the process of fission by 1 mg of ${ }_{92}^{240} \mathrm{U}$. Assume energy release per fission is 200 MeV .
[use Avogadro's number as $6 \times 10^{23}$ and 1 eV $=1.6 \times 10^{-19} \mathrm{...

The shortest wavelength in Balmer series of hydrogen atom spectrum is approximately equal to (use $R_H=1.097 \times 10^7 \mathrm{~m}^{-1}$ )

The radius and mass number of nucleus 1 is $R_1$ and $A_1$, respectively. The radius and mass number of nucleus 2 is $R_2$ and $A_2$, respectively. If $A_2$ is larger than $A_1$ by $2 \%$, then $R_2$ is larger than $R_1$ by

The difference in the wavelength between the maximum and minimum of Balmer series (use $R_H=1 \times 10^7 \mathrm{~m}^{-1}$ )

What is the mass number of the nucleus having radius equal to $\frac{1}{3}$ of that of ${ }^{189} \mathrm{Os}$ ?

Considering the Bohr's model of hydrogen atom, the ratio of velocities of electrons orbiting in the 4th orbit to that in the 9 th orbit is

The range of the nuclear force is

As the mass number $A$ increases, which of the following quantities related to a nucleus does not change?

If the series limit frequency of Balmer series is $v_B$, then the series limit frequency of the Brackett series is

Which of the following interaction is responsible for beta decay?

Consider a nucleus ${ }_{30}^{60} \mathrm{X}$. Its approximate density is (take, $1 \mathrm{amu}=1.6 \times 10^{-27} \mathrm{~kg}, R_0=1.2 \times 10^{-15} \mathrm{~m}$ )

Half-life of radioactive sample is 24 h . If a newly prepared radioactive sample shows 4 times the allowed and safe value of radio activity, the minimum time after which one can work safely with the source is

The shortest wavelength in Lyman series is $912 \mathop {\rm{A}}\limits^{\rm{o}}$. Then, the longest wavelength in the series must be

The half-life of a radiocative isotope is 30 h . How long will it take to get reduced to $12.5 \%$ of its initial amount?

If the first line in the Lyman series has wavelength $\lambda$, then the first line in Balmer series has the wavelength

A radioactive element which can decay by two processes, has half-life $t_1$ for first process and half-life $t_2$ for second process. Let $\langle t\rangle$ be the effective average-life of this element. Which of the following is correct?

In the Bohr model an electron of mass $m$ moves in a circular orbit around the proton. Considering the orbiting electron to be a circular current loop, the magnetic moment of the hydrogen atom, when the electron is in $n$th excited state. (...

Let $G, W, E$ and $S$ be relative strength of gravitational, weak-nuclear, electromagnetic and strong-nuclear forces, respectively. Which of the correct statement?

The binding energy (BE) per nucleon for an element is 7.14 MeV . If the BE of element is 28.6 MeV , then the number of nucleons in the element is

Alpha rays emitted from a radioactive substance are

The ratio of maximum to minimum wavelength in Balmer series of an hydrogenic atom is

The nuclear forces are

The half-life of a radioactive sample is 5 s . If the initial mass of the sample is 60 g , then the time required to reduce the sample to 7.5 g is

The wavelength of a spectral line emitted by hydrogen atom in the Balmer series is $\frac{16}{3 R}$
( $R$ is Rydberg constant). What is the value of the principal quantum number of the state from which the transition takes place?

In atomic scale the weakest force in nature is