Advertisements
Advertisements
प्रश्न
A set of atoms in an excited state decays ______.
विकल्प
in general to any of the states with lower energy.
into a lower state only when excited by an external electric field.
all together simultaneously into a lower state.
to emit photons only when they collide.
Advertisements
उत्तर
A set of atoms in an excited state decays in general to any of the states with lower energy.
Explanation:
When a hydrogen atom is excited, it returns to its: normal unexcited (or ground’ state) state by emitting the energy it had absorbed carli¢r, This energy is given out by the atom in the form of radiations of different wavelengths as the electron jumps down from a higher to a lower orbit. The transition from different orbits causes different wavelengths, these constitute spectral. series which ‘are characteristic of the atom emitting them. When observed through a spectroscope, these radiations are imaged as sharp and straight vertical lines of a single colour.
The spectral lines arising from the transition of an electron form a spectra series.
1. Mainly there are five series and each series is named after its discoverer as Lyman series, Balmer series, Paschen series, Bracket series and Pfund series.
2. According to Bohr's theory, the wavelength of the radiations emitted from hydrogen atom is given by
`1/λ = R[1/n_1^2 - 1/n_2^2]`
⇒ λ = `(n_1^2n_2^2)/((n_2^2 - n_1^2)R) = n_1^2/((1 - n_1^2/n_2^2)R)`
where n2 = outer orbit (electron jumps from this orbit), , = inner orbit (electron fills in this orbit)
A set of atoms in an excited state decays in general to any of the states with lower energy.
APPEARS IN
संबंधित प्रश्न
The radius of the innermost electron orbit of a hydrogen atom is 5.3 × 10−11 m. What are the radii of the n = 2 and n = 3 orbits?
The numerical value of ionization energy in eV equals the ionization potential in volts. Does the equality hold if these quantities are measured in some other units?
Suppose, the electron in a hydrogen atom makes transition from n = 3 to n = 2 in 10−8 s. The order of the torque acting on the electron in this period, using the relation between torque and angular momentum as discussed in the chapter on rotational mechanics is
When a photon stimulates the emission of another photon, the two photons have
(a) same energy
(b) same direction
(c) same phase
(d) same wavelength
Find the wavelength of the radiation emitted by hydrogen in the transitions (a) n = 3 to n= 2, (b) n = 5 to n = 4 and (c) n = 10 to n = 9.
Evaluate Rydberg constant by putting the values of the fundamental constants in its expression.
Radiation from hydrogen discharge tube falls on a cesium plate. Find the maximum possible kinetic energy of the photoelectrons. Work function of cesium is 1.9 eV.
A filter transmits only the radiation of wavelength greater than 440 nm. Radiation from a hydrogen-discharge tube goes through such a filter and is incident on a metal of work function 2.0 eV. Find the stopping potential which can stop the photoelectrons.
How are various lines of Lyman series formed? Explain on the basis of Bohr’s theory.
In Bohr model of hydrogen atom, which of the following is quantised?
Hydrogen atom has only one electron, so mutual repulsion between electrons is absent. However, in multielectron atoms mutual repulsion between the electrons is significant. How does this affect the energy of an electron in the orbitals of the same principal quantum number in multielectron atoms?
On the basis of Bohr's model, the approximate radius of Li++ ion in its ground state ifthe Bohr radius is a0 = 53 pm :
The angular momentum of electron in nth orbit is given by
An ionised H-molecule consists of an electron and two protons. The protons are separated by a small distance of the order of angstrom. In the ground state ______.
- the electron would not move in circular orbits.
- the energy would be (2)4 times that of a H-atom.
- the electrons, orbit would go around the protons.
- the molecule will soon decay in a proton and a H-atom.
Consider aiming a beam of free electrons towards free protons. When they scatter, an electron and a proton cannot combine to produce a H-atom ______.
- because of energy conservation.
- without simultaneously releasing energy in the from of radiation.
- because of momentum conservation.
- because of angular momentum conservation.
If a proton had a radius R and the charge was uniformly distributed, calculate using Bohr theory, the ground state energy of a H-atom when (i) R = 0.1 Å, and (ii) R = 10 Å.
An electron in H-atom makes a transition from n = 3 to n = 1. The recoil momentum of the H-atom will be ______.
A 100 eV electron collides with a stationary helium ion (He+) in its ground state and exits to a higher level. After the collision, He+ ions emit two photons in succession with wavelengths 1085 Å and 304 Å. The energy of the electron after the collision will be ______ eV.
Given h = 6.63 × 10-34 Js.
The radius of the nth orbit in the Bohr model of hydrogen is proportional to ______.
How much is the angular momentum of an electron when it is orbiting in the second Bohr orbit of hydrogen atom?
