Dual Nature, Atoms & Nuclei · JEE Main previous year questions

1. A.$(i)$ and $(iii)$
2. B.$(ii)$ and $(iv)$
3. C.$(ii)$ and $(iii)$
4. D.$(i)$ and $(iv)$

The threshold frequency for a metallic surface corresponds to an energy of $6.2\mathrm{eV}$ and the stopping potential for a radiation incident on this surface is $5\mathrm{V}$. The incident radiation lies in

1. A.ultra-violet region
2. B.infra-red region
3. C.visible region
4. D.$x$-ray region

An alpha nucleus of energy $\frac{1}{2}m{v}^2$ bombards a heavy nuclear target of charge $Ze$. Then the distance of closest approach for the alpha nucleus will be proportional to

1. A.$v^2$
2. B.$\frac{1}{m}$
3. C.$\frac{1}{v^4}$
4. D.$\frac{1}{Ze}$

The time taken by a photoelectron to come out after the photon strikes is approximately

1. A.$10^{-4}\mathrm{s}$
2. B.$10^{-10}\mathrm{s}$
3. C.$10^{-16}\mathrm{s}$
4. D.$10^{-1}\mathrm{s}$

When ${}_3{\mathrm{Li}}^7$ nuclei are bombarded by protons, and the resultant nuclei are ${}_4{\mathrm{Be}}^8$, the emitted particles will be

1. A.alpha particles
2. B.beta particles
3. C.gamma photons
4. D.neutrons

If the binding energy per nucleon in ${}_3^7\mathrm{Li}$ and ${}_2^4\mathrm{He}$ nuclei are $5.60\mathrm{MeV}$ and $7.06\mathrm{MeV}$ respectively, then in the reaction $$p+{}_3^7\mathrm{Li}\to 2{}_2^4\mathrm{He}$$ energy of proton must be

1. A.$28.24\mathrm{MeV}$
2. B.$17.28\mathrm{MeV}$
3. C.$1.46\mathrm{MeV}$
4. D.$39.2\mathrm{MeV}$

1. A.
2. B.
3. C.
4. D.

If the kinetic energy of a free electron doubles, it's deBroglie wavelength changes by the factor

1. A.$2$
2. B.$\frac{1}{2}$
3. C.$\sqrt{2}$
4. D.$\frac{1}{\sqrt{2}}$

A nuclear transformation is denoted by $X(n,\alpha {)}_3^7\mathrm{Li}$. Which of the following is the nucleus of element $X$ ?

1. A.${}_5^{10}\mathrm{B}$
2. B.${}^{12}{\mathrm{C}}_6$
3. C.${}_4^{11}\mathrm{Be}$
4. D.${}_5^9\mathrm{B}$

1. A.$iv$
2. B.$iii$
3. C.$ii$
4. D.$i$

If radius of the ${}_{13}^{27}\mathrm{Al}$ nucleus is estimated to be $3.6\mathrm{fermi}$ then the radius of ${}_{52}^{125}\mathrm{Te}$ nucleus is estimated to be nearly

1. A.$8\mathrm{fermi}$
2. B.$6\mathrm{fermi}$
3. C.$5\mathrm{fermi}$
4. D.$4\mathrm{fermi}$

Starting with a sample of pure ${}^{66}\mathrm{Cu}$, $\frac{7}{8}$ of it decays into $\mathrm{Zn}$ in 15 minutes. The corresponding half life is

1. A.$15\text{ minutes}$
2. B.$10\text{ minutes}$
3. C.$7\frac{1}{2}\text{ minutes}$
4. D.$5\text{ minutes}$

According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal $Vs$ the frequency of the incident radiation gives a straight line whose slope

1. A.depends both on the intensity of the radiation and the metal used
2. B.depends on the intensity of the radiation
3. C.depends on the nature of the metal used
4. D.is the same for all metals and independent of the intensity of the radiation

The work function of a substance is $4.0\mathrm{eV}$. The longest wavelength of light that can cause photo-electron emission from this substance is approximately.

1. A.$310\mathrm{nm}$
2. B.$400\mathrm{nm}$
3. C.$540\mathrm{nm}$
4. D.$220\mathrm{nm}$

The binding energy per nucleon of deuteron $\left({}_1^{2}H\right)$ and helium nucleus $\left({}_2^{4}He\right)$ is $1.1\mathrm{MeV}$ and $7\mathrm{MeV}$ respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is

1. A.$23.6\mathrm{MeV}$
2. B.$26.9\mathrm{MeV}$
3. C.$13.9\mathrm{MeV}$
4. D.$19.2\mathrm{MeV}$

An $\alpha$-particle of energy $5\mathrm{MeV}$ is scattered through $180^{\circ }$ by a fixed uranium nucleus. The distance of closest approach is of the order of

1. A.$10^{-12}\mathrm{cm}$
2. B.$10^{-10}\mathrm{cm}$
3. C.$1\mathrm{A}$
4. D.$10^{-15a}\mathrm{cm}$

A nucleus disintegrated into two nuclear parts which have their velocities in the ratio of $2:1$. The ratio of their nuclear sizes will be

1. A.$3^{1/2}:1$
2. B.$1:2^{1/3}$
3. C.$2^{1/3}:1$
4. D.$1:3^{1/2}$

If $13.6\mathrm{eV}$ energy is required to ionize the hydrogen atom, then the energy required to remove an electron from $n=2$ is

1. A.$10.2\mathrm{eV}$
2. B.$0\mathrm{eV}$
3. C.$3.4\mathrm{eV}$
4. D.$6.8\mathrm{eV}$.

Sodium and copper have work functions $2.3\mathrm{eV}$ and $4.5\mathrm{eV}$ respectively. Then the ratio of the wavelengths is nearest to

1. A.$1:2$
2. B.$4:1$
3. C.$2:1$
4. D.$1:4$

If $N_0$ is the original mass of the substance of half-life period $t_{1/2}=5$ years, then the amount of substance left after $15$ years is

1. A.$N_0/8$
2. B.$N_0/16$
3. C.$N_0/2$
4. D.$N_0/4$