The Uncertainty Principle

Q.

Why electron can not exist in the nucleus of an atom?

Q.

Uncertainty in the Position of an Electron (mass $9.1\times {10}^{-31}\mathrm{kg}$) moving with a velocity of $300{\mathrm{ms}}^{-1}$, Accurate up to $0.001\%$ will be:

Q. In the figure shown, $O$ is a point source of light and $S$ is a screen placed at a distance $L$ from the source. The intensity of light at point $\text{A}$ on the screen due to the source is $81I$ , where $I$ is some unit. Now a large mirror $\left(M\right)$ is placed behind the source at a distance $L$ from it. The mirror reflects $100\%$ of the light energy incident on it. The intensity at point $A$ is $nI.$ The value of $n$ is (integer only)

Q.

The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from n = 2 to n = 1 state is:

1. 194.8 nm

2. 490.7 nm

3. 913.3 nm

4. 121.8 nm

Q.

State Heisenbergs Uncertainty Principle.

Q. Consider a sphere of radius $R$ exposed to radiation of intensity $I$ as shown in figure. If surface of sphere is partially reflecting with reflection coefficient is $0.3$, then radiation force experienced is

1. $\frac{\pi R^{2}I}{c}$
2. $\frac{1.7\pi R^{2}I}{c}$
3. $\frac{0.3\pi R^{2}I}{c}$
4. $\frac{1.3\pi R^{2}I}{c}$

Q.

What do you mean by uncertainty?

Q. The de-Broglie wavelength of an electron in the first Bohr orbit of circumference $2\pi r$ is

1. $2\pi r$
2. $\pi r$
3. $\frac{1}{2}\pi r$
4. $\frac{1}{4}\pi r$

Q. An $\alpha -$particle of energy $3\text{MeV}$ is scattered through ${180}^{\circ }$ by gold nucleus. The distance of the closest approach is of the order of -

The atomic number of gold is $79$.

1. ${10}^{-11}\text{cm}$
2. ${10}^{-16}\text{cm}$
3. ${10}^{-13}\text{cm}$
4. ${10}^{-19}\text{cm}$

Q.

What is uncertain in the Uncertainty Principle?

Q. Light with an average flux of $10{\text{W cm}}^{-2}$ falls on a non-reflecting surface at normal incidence having surface area $40{\text{cm}}^2$. The energy received by the surface during time span of $2$ minutes is

1. $24\text{kJ}$
2. $240\text{J}$
3. $12\text{kJ}$
4. $48\text{kJ}$

Q. We wish to see inside the atom. Assuming the atom to have a diameter of $100\text{pm}$, this means that one must be able to resolve a width of say $10\text{pm}$. If an electron-micro scope is used, the minimum electron energy required is about. (Assume the wavelength of light used in an electron microscope is nearly equal to the resolving power of the electron microscope.)

1. $15\text{keV}$
2. $1.5\text{keV}$
3. $150\text{keV}$
4. $1.5\text{MeV}$

Q. An excited atom gives up its excess energy by emitting a photon of certain characteristic frequency. The average time period that elapses between the excitation of an atom and the time it radiates is $1.0\times {10}^{-8}s$. What is the inherent uncertainty in the frequency of the photon?

1. $8\times {10}^{6}Hz$
2. $8\times {10}^{8}Hz$
3. $8\times {10}^{9}Hz$
4. $8\times {10}^{7}Hz$

Q. An $\text{X}$-ray tube operates at $20\text{kV}.$ A particular electron loses $5\%$ of its kinetic energy to emit an $\text{X}$-ray photon at the first collision. Find the wavelength corresponding to this photon.

1. $2.56\text{nm}$
2. $1.24\text{nm}$
3. $3.78\text{nm}$
4. $0.45\text{nm}$

Q. The de Broglie wavelength of an electron having $320\text{eV}$ of energy is nearly $(1\text{eV}=1.6\times {10}^{-19}\text{J}$, mass of electron $=9.1\times {10}^{-31}\text{kg}$, Planck's constant $=6.6\times {10}^{-34}\text{Js})$

1. $70\stackrel{\circ }{\text{A}}$
2. $0.7\stackrel{\circ }{\text{A}}$
3. $1.4\stackrel{\circ }{\text{A}}$
4. $14\stackrel{\circ }{\text{A}}$

Q. For a white body, the reflective power is -

1. $0.5$
2. $0.7$
3. $0.8$
4. $1.0$

Q. Light with an energy flux of $25\times {10}^{4}W{m}^{-2}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is $15c{m}^2$, the average force exerted on the surface is

1. $1.25\times {10}^{-6}N$
2. $2.50\times {10}^{-6}N$
3. $1.20\times {10}^{-6}N$
4. $3.0\times {10}^{-6}N$

Q. An $EM$ wave of intensity $I$ falls on a surface kept in vacuum and exerts radiation pressure $p$ on it. Whether the following statements are true or not?

i) Radiation pressure is $I/c$ if the wave is totally absorbed.

ii) Radiation pressure is $I/c$ if the wave is totally reflected.

iii) Radiation pressure is $2I/c$ if the wave is totally reflected.

iv) Radiation pressure is in the range $I/c<p<2I/c$

Q.

Is Heisenberg Uncertainty Principle True

Q.

When was the Heisenberg uncertainty principle developed?

Q.

Who proposed the theory of the Feynman diagram?

Q. A typical atomic nucleus is about $5.0\times {10}^{-15}m$ in radius. Using the uncertainty principle, what should be the lower limit on momentum, that a particle must have if it is to be a part of a nucleus?

1. $1.1\times {10}^{-20}kgm/s$
2. $2.2\times {10}^{-20}kgm/s$
3. $4.4\times {10}^{-20}kgm/s$
4. No lower limit

Q.

Is Heisenberg uncertainty principle wrong

Q.

1. Position of electron can be found exactly if its momentum is known.
2. Momentum of an electron can be found exactly if its position is known.
3. The lowest energy of an atom can hold only one electron.
4. Light has a dual nature- wave and photon.
5. There is a limit to the accuracy of the measurement of subatomic particles.

Q.

State Heisenbergs uncertainty principle.

Q. In the figure shown, $O$ is a point source of light and $S$ is a screen placed at a distance $L$ from the source. The intensity of light at point $\text{A}$ on the screen due to the source is $81I$ , where $I$ is some unit. Now a large mirror $\left(M\right)$ is placed behind the source at a distance $L$ from it. The mirror reflects $100\%$ of the light energy incident on it. The intensity at point $A$ is $nI.$ The value of $n$ is (integer only)

Q.

Is the Heisenberg Uncertainty Principle True?

Q.

What does Heisenbergs uncertainty principle imply about the behavior of an electron?

Q. Light with an energy flux of $25\times {10}^4{\text{Wm}}^{-2}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is $15{\text{cm}}^2$, the average force exerted on the surface is :

1. $1.25\times {10}^{-6}\text{N}$
2. $2.50\times {10}^{-6}\text{N}$
3. $1.15\times {10}^{-6}\text{N}$
4. $3.0\times {10}^{-6}\text{N}$

Q. A light of wavelength $650\text{nm}$ falls on a surface at an angle ${60}^{\circ }$ and bounces back at the same angle from the normal. If the reflectivity of the surface is $50\%$ and intensity of light is $100{\text{W/m}}^2$, find the pressure experienced by the surface due to the reflected radiation.

1. $1.67\times {10}^{-7}{\text{N/m}}^2$
2. $1.67\times {10}^{-5}{\text{N/m}}^2$
3. $1.67\times {10}^{-9}{\text{N/m}}^2$
4. $1.67\times {10}^{-2}{\text{N/m}}^2$