Physics M.C.Q (1 Marks)

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.

1. To heat the cathode

Explanation:
When current passes through the filament it gets heated. 
The heated filament transfers it's heat to the cathode plate.

2. 7

Explanation:
Atomic number of any element is equal to number of proton or number of electron
Atomic Number = no. of proton = no of electron.

1. Balmer.

2. 108.8eV.

4. Plum pudding, planetary, Bohr

Explanation:
J.J. Thomson proposed plum pudding model in 1904. Ernest Rutherford introduced the planetary model of an atom in 1911 which was modified by Neils Bohr in 1913 as Bohr model of an atom.
Order in which the atomic models were advanced: Plum pudding, planetary, Bohr.

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.

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. Coulomb force

Explanation:
Coulomb force is responsible for scattering of particles. When the alpha particles (positive in charge) get closer to the nucleus, which is positive in charge, they get repelled through various angles.

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. Gravitational field

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

2. Er.

1. Light

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

1. 1.

4. All of these.

3. Electric potential

Explanation:
In the oscilloscope, the signal to be studied is first amplified and then applied to the vertical plate to deflect the beam vertically and at the same time, a voltage that increases linearly with time is applied to the horizontal plate thus causing the beam to be deflected horizontally. The signal applied to the vertical plate is thus displayed on the screen as a function of time.
Hence focussing of beam on screen is achieved by changing electric potential or the voltage with time across the horizontal plate.

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.

1. J.J. Thomson.

4. Energy

1. Four times, it ground state radius.

4. P. E. increases, T.E. increases.

1. Gaseous state

Explanation:
Solids and liquids give continuous and line spectra. Only gases are known to give band spectra.

1. Element

Explanation:
An element is a substance consisting of atoms which all have the same number of proton i.e. the same atomic number.

2. Different for different elements.

3. 3.

2. Visible

Explanation:
Balmer series lies in the visible spectrum.

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.

4. 2

Explanation:
Atomic number of any element is equal to number of protons or number of electrons.
Atomic no = no of proton  = no of electron.

3. Neutron

4. De – Broglie concluded that wavelengths of matter waves can be quantized.

Explanation:
de – Broglie concluded his modification of Bohr’s second postulate by stating that the wavelengths of matter waves can be quantized.
This implies that the electrons can exist in those orbits which had a complete set of several wavelengths.

3. It could not explain scattering of α-particles.

2. Bohr theory

Explanation:
Niels Bohr explained the line spectrum of the hydrogen atom with the assumption that electrons revolved around an atom in circular orbits and that the orbit closer to the nucleus represented the ground state and the farther orbits represented the higher levels of energy.

3. An electric as well as a magnetic field

Explanation:
Cathode ray consists of beams of electrons that constitute current and, hence magnetic field. We know electric field is produced by a charge, whether it is stationary or moving. So electric field will also be present inside the tube.

1. Quantized

Explanation:
The first postulate of Bhor theory is that the orbital momentum of the electron is quantized ie, L = mvr = nh where h is Drac constant.

4. Both (A) and (C)

Explanation:
Fluroscent lamp and compact fluroscent lamp works based on the low pressure gas discharge principle.
The glass tube if low pressure gas discharge lamp is filled with noble gas at low pressure and small quantity of mercury.

3. By changing the negative potential on grid

Explanation:
Since the brightness or intensity of the display depends on the number of electrons that strike the screen, the control grid is used to control the brightness of the CRT.

2. Balmer series.

1. A free neutron can transform itself into photon

Explanation:
In beta minus decay, a neutron decays into a proton, an electron.
A free neutron is unstable, decaying to a proton, electron and antineutrino.
Inside a nucleus, a proton can transform into a neutron via inverse beta.

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.

4. failed to explain larger atoms

Explanation:
Bohr's model can only clearly explain hydrogen or hydrogen-like atoms, it fails when applied to larger and heavier atoms like iron, gold, mercury, etc.

1. 1000V

Explanation:
The electrons are accelerated by a second anode at high potential, more than 500V