CBSE Questions for Class 12 Medical Physics Atoms Quiz 5 - MCQExams.com

According to Bohr model, the diameter of first orbit of hydrogen atom will be
  • $$ 1 A^{\circ}$$
  • $$ 0.529 A^{\circ}$$
  • $$ 2.25 A^{\circ}$$
  • $$ 0.725 A^{\circ}$$
The radius of shortest orbit in one electron system is $$18 $$pm. It may be
  • $$\displaystyle_{1}^{1}\textrm{H}$$
  • $$\displaystyle_{1}^{2}\textrm{H}$$
  • $$\displaystyle He^{+}$$
  • $$\displaystyle Li^{++}$$
A cathode ray tube  has a potential difference of V volt between the cathode and the anode. The speed of cathode rays is given by
  • $$\displaystyle 6\times 10^{-5}\sqrt{V}cm/s$$
  • $$\displaystyle 6\times 10^{5}\sqrt{V}m/s$$
  • $$\displaystyle 6\times 10^{7}\sqrt{V}cm/s$$
  • $$\displaystyle 6\times 10^{3}\sqrt{V}m/s$$
If the transition of electron takes place from $$n$$=4 state, then the maximum number of spectral lines obtained for transition to ground state will be
  • $$6$$
  • $$12$$
  • $$18$$
  • $$24$$
The collector plate in an experiment on photoelectric effect is kept vertically above the emitter plate. Light source is made on and a saturation photocurrent is recorded. An electric field is switched on which has a vertically downward direction.
  • The photocurrent will increase
  • The kinetic energy of the electrons will increase
  • The stopping potential will decrease
  • The threshold wavelength will increase
When a photon stimulates the emission of another photon, the two photons have
  • Same energy
  • Same direction
  • Same phase
  • Same wavelength
Which of the following products in a hydrogen atom are independent of the principal quantum number $$'n\ '$$? The symbols have their usual meanings.
  • $$vn$$
  • $$Er$$
  • $$En$$
  • $$vr$$
Let $$A_{n}$$ be the area enclosed by the $$n$$th orbit in a hydrogen atom. The graph of $$In(A_{n}/A_{1})$$ against $$In(n)$$
  • will pass through the origin.
  • will be a straight line with slope.
  • will be a monotonically increasing nonlinear curve.
  • will be a circle.
On decreasing principal quantum number $$n$$, the values of $$r$$ and $$v$$ will
  • decrease
  • increase
  • $$r$$ will increase by $$v$$ will decrease
  • $$r$$ will decrease by $$v$$ will increase
The maximum number of electrons in a sub-shell is
  • $$2(2l+1)$$
  • $$2l+1$$
  • $$2l$$
  • $$2l-1$$
The spin of electron, proton and neutron is
  • $$h$$
  • $$\displaystyle \frac{h}{2}$$
  • zero
  • none of these
The possible values of $$m_{l}$$ are
  • from -1 to +1
  • from 0 to 8
  • from zero to +1
  • none of these
A hydrogen atom is in the $$d$$-state. The values of $$m$$ for this state are
  • $$-1, 0, 1$$
  • $$-3, -1, 0, 1, 3$$
  • $$2, 1, 0$$
  • $$-2, -1, 0, 1, 2$$
The values of $$n_{1}$$ and $$n_{2}$$ for Pfund's series are
  • $$n_{1}=4, n_{2}=5,6,7....$$
  • $$n_{1}=5, n_{2}=6,7$$
  • $$n_{1}=3, n_{2}=4,5,6....$$
  • $$n_{1}=2, n_{2}=3,4,5....$$
The maximum possible values of magnetic orbital quantum number ($$m_{l})$$ are
  • $$(2l + 1)$$
  • $$2l $$
  • $$(2l - 1)$$
  • zero
The maximum number of electrons in a shell is
  • $$n^{2}$$
  • $$2n^{2}$$
  • $$2n$$
  • $$n$$
The possible values of orbital quantum numbers are:
[$$n$$ is the principle quantum number]
  • from 0 to ($$n$$-1)
  • from 0 to $$n$$
  • from 0 to ($$n$$+1)
  • all of the above
The photoelectric effect proves that light consists of 
  • Photons
  • Electrons
  • Electromagnetic waves
  • Mechanical waves
What would be the appropriate quantum number $$n$$ $$A^{0}$$ for circular orbits of radius $$13.2$$ $$A^{0}$$ in hydrogen?
  • $$6$$
  • $$7$$
  • $$5$$
  • $$4$$
In which of the following systems, the radius of first orbit ($$n=1$$) is minimum
  • Hydrogen
  • Deuterium atom
  • Singly ionized helium
  • Doubly ionised lithium
The hyperfine lines in the spectrum is related to 
  • Zeeman effect
  • Stark effect
  • Lande's splitting
  • nuclear magnetic spin
The potential difference between the wire and the cylinder produces an electric field of $$2\times10^{4} Vm^{-1}$$ at a distance of $$1.2 cm$$ from the wire
155818_21f971c0f58e4da6a91a867802405a72.png
  • $$360 V$$
  • $$180 V$$
  • $$200 V$$
  • $$240 V$$
If the radius of first Bohr orbit is $$r$$, then the radius of second orbit will be
  • 2$$r$$
  • $$\dfrac{r}{2}$$
  • 4$$r$$
  • $$\sqrt{2}{r}$$
Which of the following does not fit into a group
  • Photon
  • Graviton
  • Proton
  • Meson
Suppose a particle $$a$$ of charge $$2e$$ and mass $$2m_{e}$$ ($$m_{e}$$ being mass of electron) revolves around the proton in nearest allowed circular orbit of radius r. If the radius of first Bohr orbit for the electron is $$A_{0}$$, then the relation between $$r$$ and $$a_{0}$$ is 
  • $$a_{0}$$ = $$4r$$
  • $$a_{0}$$ =$$8r$$
  • $$a_{0}$$ = $$2r$$
  • $$a_{0}$$ = $$\displaystyle\ \frac{r}{4}$$
According to Geiger-Nuttal Law the curve between $$log \lambda$$ and $$log R$$ will be 
When $$Z$$ is doubled in an atom, which of the following statement is consistent with Bohr's theory?
  • Energy of a state is doubled
  • Radius of an orbit is doubled
  • Velocity of electrons in the orbit is doubled
  • Radius of an orbit is quadrupled.
The ratio of radii of first orbit of hydrogen atom and the second orbit of singly ionised helium atom will be
  • $$1:2$$
  • $$4:1$$
  • $$1:4$$
  • $$8:1$$
How many protons and neutrons are there in the nuclei of $$^{25}_{12}Mg$$
  • 12, 13
  • 13, 12
  • 25, 12
  • 12, 25
Hydrogen atoms are excited from ground state to the state of principal quantum number $$4$$. Then, the number of spectral lines observed will be
  • $$3$$
  • $$6$$
  • $$5$$
  • $$2$$
Which of the following parameters are the same for all hydrogen-like atoms and ions in their ground states?
  • Radius of the orbit
  • Speed of the electron
  • Energy of the atom
  • Orbital angular momentum of the electron
What is the angular momentum of an electron in Bohr's hydrogen atom whose energy is $$-3.4\space eV$$?
  • $$L = \displaystyle\frac{h}{\pi}$$
  • $$L = \displaystyle\frac{4h}{\pi}$$
  • $$L = \displaystyle\frac{3h}{\pi}$$
  • $$L = \displaystyle\frac{5h}{\pi}$$
There are seven orbitals in a subshell then the value of $$l$$ for it will be
  • $$l=4$$
  • $$l=3$$
  • $$l=2$$
  • $$l=1$$
The electron in a hydrogen atom jumps from the ground state to the higher energy where its velocity is reduced to one-third of its initial value. If the radius of the orbit in the ground state is $$r$$, the radius of new orbit will be
  • $$3r$$
  • $$9r$$
  • $$\displaystyle\frac{r}{3}$$
  • $$\displaystyle\frac{r}{9}$$
Two electrons in an atom are moving in orbit of radii $$R$$ and $$9R$$ respectively. The ratio of their frequencies will be
  • $$1:8$$
  • $$8:1$$
  • $$1:27$$
  • $$27:1$$
Whenever a hydrogen atom emits a photon in the Balmer series
  • It need not emit any more photon
  • It may emit another photon in the Paschen series
  • It must emit another photon in the Lyman series
  • It may emit another photon on the Balmer series
The radius of the Bohr orbit in the ground state of hydrogen atom is $$0.5\mathring{A}$$. The radius of the orbit of the electron in the third excited state of $$He^+$$ will be
  • $$8\mathring{A}$$
  • $$4\mathring{A}$$
  • $$0.5\mathring{A}$$
  • $$0.25\mathring{A}$$
In the above figure, $$E_1$$ to $$E_6$$ represent some of the energy levels of an electron in the hydrogen atom.
Which one of the following transitions produces a photon of wavelength in the ultra-violet region of the electromagnetic spectrum?
169641.png
  • $$E_2-E_1$$
  • $$E_3-E_2$$
  • $$E_4-E_3$$
  • $$E_6-E_4$$
The approximate value of quantum number $$'n\ '$$ for the circular orbit of hydrogen of $$0.0001\space mm$$ in diameter is
  • $$1000$$
  • $$60$$
  • $$10000$$
  • $$31$$
How many revolutions does an electron complete in one second in the first orbit of hydrogen atom?
  • $$6.62\times10^{15}$$
  • $$6.62\times10^{5}$$
  • $$6.62\times10^{10}$$
  • $$1.62\times10^{15}$$
The electric potential energy between a proton and an electron is given by $$U=U_0ln\dfrac{r}{r_0}$$, where $$r_0$$ is a constant. Assuming Bohr's model to be applicable, write the variation of $$'r\ '$$ with $$n$$, $$n$$ being the principal quantum number.
  • $$r_n \propto n$$
  • $$r_n \propto 1/n$$
  • $$r_n \propto n^2$$
  • $$r_n \propto 1/n^2$$
A beam of $$13.0\space eV$$ electrons is used to bombard gaseous hydrogen. The series obtained in emission spectra is/are
  • Lyman series
  • Balmer series
  • Brackett series
  • All of these
In Bohr's model of hydrogen atom, 
  • The radius of $$nth$$ orbit is proportional to $$n^2$$
  • The total energy of electron in $$n^{th}$$ orbit is proportional to $$n$$
  • The angular momentum of the electron in an orbit is an integral multiple of $$h/2\pi$$
  • The magnitude of the potential energy of electron in any orbit is greater than its Kinetic energy
Which of the following is true when Bohr gave his model for hydrogen atom?
  • It was not known that hydrogen lines could be explained as differences of terms like $$R/n^2$$ with $$R$$ being a constant and $$n$$ an integer
  • It was not known that positive charge is concentrated in a nucleus of small size
  • It was known that radiant energy occurred in energy bundles defined by $$hv$$ with $$h$$ being a constant and $$v$$ a frequency
  • Bohr knew terms like $$R/n^2$$ and in the process of choosing allowed the orbits to fit them, he got angular momentum = $$nh/2\pi$$ as deduction
If a nucleus such as $$^{226}Ra$$, that is initially at rest, undergoes $$\alpha-decay$$, then which of the following statement is true?
  • The alpha particle has more kinetic energy then the daughter nucleus
  • The alpha particle has less kinetic energy then the daughter nucleus
  • The alpha particle and daughter nucleus both have same kinetic energy
  • We cannot say anything about kinetic energy of alpha particle and daughter nucleus
Difference between $$nth$$ and $$(n+1)th$$ Bohr's radius of hydrogen atom is equal to $$(n-1)th$$ Bohr's radius. The value of $$n$$ is
  • $$1$$
  • $$2$$
  • $$3$$
  • $$4$$
The radius of hydrogen atom in the ground state is $$5.3\times10^{-11} m$$. When struck by an electron, its radius is found to be $$21.2\times10^{-11}m$$. The principal quantum number of the final state will be
  • $$2$$
  • $$3$$
  • $$4$$
  • $$16$$
The angular momentum of an electron in an orbit is quantized because it is a necessary condition for the compatibility with
  • Wave nature of electron
  • Particle nature of electron
  • Pauli's exclusion behaviour
  • None of these
If elements with principal quantum number $$n>4$$ were not allowed in nature, the number of possible elements would have been
  • $$32$$
  • $$60$$
  • $$18$$
  • $$4$$
How can the rate of emission of electrons in a cathode ray tube can be increased?
  • Increasing resistance of filament 
  • Increasing filament current
  • Decreasing filament current 
  • Increasing magnetic field inside tube
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