Physics M.C.Q [1M]

The Rutherford a-particle experiment shows that most of the a-particles pass through almost unscattered while some are scattered through large angles. What information does it give about the structure of the atom

(a) Atom is hollow

(b) The whole mass of the atom is concentrated in a small centre called nucleus

(c) Nucleus is positively charged

(d) All the above

The wavelength of yellow line of sodium is 5896 Å. Its wave number will be

(a) 50883 × 1010 per second	(b) 16961 per cm
(c) 17581 per cm	(d) 50883 per cm

In the following transitions, which one has higher frequency

(a) 3 – 2

(b) 4 – 3

(c) 4 – 2

(d) 3 – 1

Radius of the first orbit of the electron in a hydrogen atom is 0.53 Å. So, the radius of the third orbit will be

(a) 2.12 Å

(b) 4.77 Å

(c) 1.06 Å

(d) 1.59 Å

For principal quantum number n = 3, the possible values of orbital quantum number ‘l’ are

(a) 1, 2, 3

(b) 0, 1, 2, 3

(c) 0, 1, 2

(d) –1, 0, +1

Which of the following is true for number of spectral lines in going form Layman series to Pfund series

(a) Increases	(b) Decreases
(c) Unchanged	(d) May decreases or increases

Rutherford’s a - particle experiment showed that the atoms have

(a) Proton

(b) Nucleus

(c) Neutron

(d) Electrons

According to classical theory, the circular path of an electron in Rutherford atom is

(a) Spiral

(b) Circular

(c) Parabolic

(d) Straight line

According to the Rutherford’s atomic model, the electrons inside the atom are

(a) Stationary

(b) Not stationary

(c) Centralized

(d) None of these

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true

(a) Its kinetic energy increases and its potential and total energies decrease

(b) Its kinetic energy decreases, potential energy increases and its total energy remains the same

(c) Its kinetic and total energies decrease and its potential energy increases

(d) Its kinetic, potential and total energies decreases

In Bohr model of hydrogen atom, the ratio of periods of revolution of an electron in n = 2  and n = 1 orbits is

(a) 2 : 1

(b) 4 : 1

(c) 8 : 1

(d) 16 : 1

Which of the following statements are true regarding Bohr's model of hydrogen atom

(I)  Orbiting speed of electron decreases as it shifts to  discrete orbits away from the nucleus

(II)  Radii of allowed orbits of electron are proportional to the principal quantum number

(III) Frequency with which electrons orbits around the nucleus in discrete orbits is inversely proportional to the principal quantum number

(IV)  Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits Select correct answer using the codes given below

Codes :

(a) I and III

(b) II and IV

(c) I, II and III

(d) II, III and IV

In hydrogen atom, if the difference in the energy of the electron in n = 2  and n = 3  orbits is E, the ionization energy of hydrogen atom is

(a) 13.2 E

(b) 7.2 E

(c) 5.6 E

(d) 3.2 E

The energy of hydrogen atom in its ground state is – 13.6 eV. The energy of the level corresponding  to the quantum number n is equal 5 is

(a) – 5.40 eV

(b) – 2.72 eV

(c) – 0.85 eV

(d) – 0.54 eV

If scattering particles are 56 for 90°  angle then this will be at 60°  angle

(a) 224

(b) 256

(c) 98

(d) 108

The fact that photons carry energy was established by

(a) Doppler's effect	(b) Compton's effect
(c) Bohr's theory	(d) Diffraction of light

Which of the following phenomena suggests the presence of electron energy levels in atoms

(a) Radio active decay	(b) Isotopes
(c) Spectral lines	(d) a -particles scattering

The energy of electron in first excited state of H-atom is  -3.4 eV  its kinetic energy is

(a) – 3.4 eV

(b) + 3.4 eV

(c) – 6.8 eV

(d) 6.8 eV

In Bohr's model of hydrogen atom, let PE represents potential energy and TE the total energy. In going to a higher level

(a) PE decreases, TE increases	(b) PE increases, TE increases
(c) PE decreases, TE decreases	(d) PE increases, TE decreases

Which one of these is non-divisible

(a) Nucleus

(b) Photon

(c) Proton

(d) Atom

Number of spectral lines in hydrogen atom is    

(a) 3

(b) 6

(c) 15

(d) Infinite

Hydrogen atom excites energy level from fundamental state to n = 3. Number of spectrum lines according to Bohr, is

(a) 4

(b) 3

(c) 1

(d) 2

Minimum energy required to takeout the only one electron from ground state of   is

(a) 13.6 eV

(b) 54.4 eV

(c) 27.2 eV

(d) 6.8 eV

The splitting of line into groups under the effect of electric or magnetic field is called

(a) Zeeman's effect	(b) Bohr's effect
(c) Heisenberg's effect	(d) Magnetic effect

In Rutherford scattering experiment, what will be the correct angle for α scattering for an impact parameter b = 0

(a) 90°

(b) 270°

(c) 0°

(d) 180°

Hydrogen atom emits blue light when it changes from n = 4 energy level to the n = 2 level. Which colour of light would the atom emit when it changes from the n = 5 level to the n = 2 level

(a) Red

(b) Yellow

(c) Green

(d) Violet

Hydrogen atoms are excited from ground state of the principal quantum number 4. Then the number of spectral lines observed will be

(a) 3

(b) 6

(c) 5

(d) 2

The ionisation energy of hydrogen atom is 13.6 eV. Following Bohr's theory, the energy corresponding to a transition between the 3rd and the 4th orbit is

(a) 3.40 eV

(b) 1.51 eV

(c) 0.85 eV

(d) 0.66 eV

To explain his theory, Bohr used

(a) Conservation of linear momentum

(b) Conservation of angular momentum

(c) Conservation of quantum frequency

(d) Conservation of energy

An electron in the n = 1 orbit of hydrogen atom is bound by 13.6 eV energy is required to ionize it is

(a) 13.6 eV

(b) 6.53 eV

(c) 5.4 eV

(d) 1.51 eV

The third line of Balmer series of an ion equivalent to hydrogen atom has wavelength of 108.5 nm. The ground state energy of an electron of this ion will be

(a) 3.4 eV

(b) 13.6 eV

(c) 54.4 eV

(d) 122.4 eV

The absorption transitions between the first and the fourth energy states of hydrogen atom are 3. The emission transitions between these states will be    

(a) 3

(b) 4

(c) 5

(d) 6

Ratio of the wavelengths of first line of Lyman series and first line of Balmer series is

(a) 1: 3

(b) 27 : 5

(c) 5 : 27

(d) 4 : 9

In a hydrogen atom, which of the following electronic transitions would  involve the maximum energy change

(a) From n = 2 to n = 1	(b) From n = 3 to n = 1
(c) From n = 4 to n = 2	(d) From n = 3 to n = 2

If the ionisation potential of helium atom is 24.6 volt, the energy required to ionise it will be

(a) 24.6 eV

(b) 24.6 V

(c) 13.6 V

(d) 13.6 eV

The ratio of the frequencies of the long wavelength limits of Lyman and Balmer series of hydrogen spectrum is

(a) 27 : 5

(b) 5 : 27

(c) 4 : 1

(d) 1 : 4

he half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its  th part

(a) 12 h

(b) 16 h

(c) 48 h

(d) 192 h

In Bohr model of the hydrogen atom, the lowest orbit corresponds to

(a) Infinite energy	(b) The maximum energy
(c) The minimum energy	(d) Zero energy

When a hydrogen atom is raised from the ground state to an excited state

(a) P.E. increases and K.E. decreases

(b) P.E. decreases and K.E. increases

(c) Both kinetic energy and potential energy increase

(d) Both K.E. and P.E. decrease

A hydrogen atom (ionisation potential 13.6 eV) makes a transition from third excited state to first excited state. The energy of the photon emitted in the process is

(a) 1.89 eV

(b) 2.55 eV

(c) 12.09 eV

(d) 12.75 eV

The spectral series of the hydrogen spectrum that lies in the ultraviolet region is the

(a) Balmer series

(b) Pfund series

(c) Paschen series

(d) Lyman series

In any Bohr orbit of the hydrogen atom, the ratio of kinetic energy to potential energy of the electron is

(a) 1/2

(b) 2

(c) -1/2

(d)  -2

The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is

(a) – 1

(b) 2

(c) 1 : 2

(d) None of these

In the above figure D and E respectively represent

(a) Absorption line of Balmer series and the ionization potential of hydrogen

(b) Absorption line of Balmer series and the wavelength lesser than lowest of the Lyman series

(c) Spectral line of Balmer series and the maximum wavelength of Lyman series

(d) Spectral line of Lyman series and the absorption of greater wavelength of limiting value of Paschen series

In the n^th orbit, the energy of an electron  for hydrogen atom. The energy required to take the electron from first orbit to second orbit will be

(a) 10.2 eV

(b) 12.1 eV

(c) 13.6 eV

(d) 3.4 eV

If one starts with one curie of radioactive substance (T_1/2 = 12 hrs) the activity left after a period of 1 week will be about

(a) 1 curie

(b) 120 micro curie

(c) 60 micro curie

(d) 8 mili curie

Assertion  : Radioactive nuclei emit   particles.

Reason      : Electrons exist inside the nucleus.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Rest mass energy of an electron is 0.54 MeV. If velocity of the electron is 0.8 c, then K.E. of the electron is

(a) 0.36 MeV

(b) 0.41 MeV

(c) 0.48 MeV

(d) 1.32 MeV

The wavelength K_a X-rays produced by an X-ray tube is 0.76 Å. The atomic number of anticathode material is

(a) 82

(b) 41

(c) 20

(d) 10

Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be

(a) 20 minutes

(b) 40 minutes

(c) 30 minutes

(d) 25 minutes