Physics M.C.Q [1M]

4. The stability of atom was established by the model.

Explanation:

According to Rutherford model as he was not able to explain stability of atom.

4. Energy

3. 13.6 eV,-27.2 eV

3. The property to cause fluorescence

4. Gravitational field

Explanation:

Gravitational field applies minimum force on cathode rays because gravitational forces are proportional to masses but not charges.

4. An electron will absorb energy when jumping from the 1^st orbit to the 3^rd orbit.

Explanation:

An electron will absorb energy when jumping from the 1st orbit to the 3rd orbit.

Only by absorbing energy, an electron will be able to jump from the first orbit to the third orbit in the atomic spectrum.

3. Neil Bohr

Explanation:

Neil Bohr proposed the concept of stationary orbits in 1913, which is now called the Bohr model of atom. The electron can only orbit stably, without radiating, in certain orbits at a certain discretesct of distance from the nucleus.

2. Absorption line spectrum is characteristic of the element

Explanation:

Line respectrum is characteristic of the element because it obtained of atoms only. Continous spectrum is characteristics of the source of light.

In the spectrum of sodium, there are two prominent yellow lines of wavelength 589.0 nm and 589.6 nm.
Absorption line spectrum is not characteristic of the element.

2. Balmer series

Explanation:

Transition from higher states to n = 2 lead to emission of radiation with wavelengths 656.3nm and 365.0nm.

These wavelengths fall in the visible region and constitute the Balmer series.

1. All the properties of the substance

Explanation:

A molecule is defined as the smallest particle which possesses all the properties of the substance.

1. Because of energy conservation.
2. Without simultaneously releasing energy in the from of radiation.

​​​​​​​Solution:

When a beam of free electrons is aiming towards free protons, then, they scatter but an electron and a proton cannot combine to produce a hydrogen atom because of energy conservation and without simultaneously releasing energy in the form of radiation.

1. The electron would not move in circular orbits.

3. The electrons, orbit would go arround the protons.

​​​​​​​Solution:

In a hydrogen atom, electron revolves around a fixed proton nucleus in circular path. This can be explained by Bohr model. But in case of ionised H-molecule which consists of two protons in nucleus and where protons are separated by a small distance of the order of angstrom, cannot be explained by Bohr model. Hence in this case the ground state the electron would not move in circular orbits, the electrons orbit would go around the protons.

2. Second line of Balmer series.

1. Spiral.

2. Balmer series.

1. from -1 to + 1

Explanation:

Values for the quantum number ml​ are -1, 0, + 1

4. Depends on the energy levels of the orbits

Explanation:

When an electron jumps from lower energy level to higher energy level it absorbs energy and when it jumps from higher energy level to lower energy level it emits energy.

So whether the electron emits or absorbs energy depends on the energy levels of the orbit

3. The transition of electrons between two energy levels.

Explanation:

The observed spectral lines are caused by the transition of electrons between two energy levels in an atom.

The emission spectrum of the hydrogen atom is divided into many spectral series, with wavelengths that are given by Rydberg’s formula.

3. J.J. Thomson

1. from 0 to (n - 1)

Explanation:

The orbital quantum number, l, divides the shells up into smaller groups of subshells called orbitals. The orbital quantum number describes shape of subshells. The principal quantum number(n) determines the possible values of l. For n = 1 i.e. K-shell there is no subshell so, l = 0 i.e. (n − 1). Hence, The possible values of orbital quantum numbers are from 0 to (n − 1).

1. –27eV, –12eV.

2. Balmer se

1. Whole of the positive charge is concentrated at the centre of atom.

2. Niels Bohr

Explanation:

Niels Bohr introduced the atomic Hydrogen model in 1913.

Neils Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another.

4. All of the above.

3. Line absorption spectrum

Explanation:

Solar spectrum is a line absorption spectrum which is also called as Fraunhofer lines of missing wavelengths.

4. 27 : 1

Explanation:

Radius is directly proportional to square of n.

Therefore, ratio of principal quantum number is 1 : 3.

Hence, ratio of frequencies is 27 : 1.

4. Both A and B are true.

Explanation:

The light emitted by one kind of atoms generally have widely separated wavelength components. When such a light is dispersed, we get certain sharp bright lines on a dark background. Such a spectrum is called line emission spectrum.The wavelength emitted by the molecules are grouped, each group being well separated from the other. The wavelengths in a group are close to one another and appear as continuous.The spectrum looks like separate bands of varying colors. Such a spectrum is called a band emission spectrum.So, line spectra are due to atoms in a gaseous state and band spectra are due to molecules.

1. Rest mass

Explanation:

A particle representing a quantum of light or other electromagnetic radiation.

A photon carries energy proportional to the radiation frequency but has zero rest mass.

1. Light

Explanation:

According to the Corpuscles theory, corpuscles are the tiny particles of light.

1. 1.

3. Cathode ray tube

Explanation:

Cathode ray tube is commonly used to convert an electrical signal into a visual signal. A cathode ray tube is a vacuum tube consisted of electron gun and a phosphorescent screen and is used to display images. It accelerates and deflects electron beam to create images.

4. All of these.

1. 4r_0.

2. Its atomic number decreases by 2

Explanation:

When an alpha particle is emitted from a radioactive source or substance, its atomic number decreases by 2 and its atomic mass decreases by 4, which is same as that of helium ion.

3. Spiral

Explanation:

According to classical theory, the circular path of the electrons is spiral.

2. 823nm.

2. Not stationary.

4. Inversely proportional to n_3.

1. Balmer.

1. 54.4eV.

1. Two diodes

2. Antiproton

Explanation:

antiparticle of proton is antiproton.

1. To provide kinetic energy to electrons

Explanation:

In a Cathode ray tube electrons comes out from cathode. After cathode, anode is placed, which as being +ively charged, accelerates electrons and provide them kinetic energy.

2. Different for different elements.

1. Must be elastic.

Explanation:

The minimum energy required to excite a hydrogen atom from its ground state to 1^st excited state is approximately 10eV. As the incident electron energy is not sufficient for excitation of the hydrogen atom so electron will not get absorbed in the hydrogen atom so it can not be an inelastic collision. Also this collision can not be partially elastic because in an partially elastic collision, there is a net loss on kinetic energy. If the energy is lost then corresponding amount of heat should have been produced but it is not so which implies that the collision is completely elastic.