Question 1
Question
In the Bohr model of the hydrogen atom, let R, V and E represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is proportional to the quantum number n?
Question 2
Question
The work function for aluminium is 4.125 eV. The cut off wavelength for photoelectric effect for Aluminium is
Answer

200 nm

300 nm

150 nm

420 nm
Question 3
Question
The electron is a hydrogen atom makes a transition from n = n1 to n = n2 state. The time period of the electron in the final state is eight times that in the initia state. Then the possible values of n1 and n2 are
Answer

n1 = 8, n2 = 2

n1 = 4, n2 = 2

n1 = 6, n2 = 2

n1 = 1, n2 = 2
Question 4
Question
Light of frequency 1.5 times the threshold frequency is incident on photosensitive material. If the frequency is halved and intensity is doubled, the photocurrent becomes
Answer

Quadrupled

Doubled

Zero

Halved
Question 5
Question
A radioactive substance has a half life of four months. Three fourth of the substance will decay in
Answer

12 months

4 months

8 months

3 months
Question 6
Question
A radio isotope has a half life of 5 years. The fraction of the atoms of this material that would decay in 15 years will be
Question 7
Question
When Boron 5B10 is bombarded by neutron, particles are emitted. The resulting nucleus has mass number
Question 8
Question
Tracer techniques make use of
Answer

neutron scattering

electron beams

lasers

radioactive isotopes
Question 9
Question
A sample of radioactive substance contains 2,828 atoms. If its half life is two days, how many atoms will be left intact in the sample after one day?
Question 10
Question
The unit of Planck’s constant is
Question 11
Question
Mean life of a radioactive element is one year. Then its half life is (years)
Question 12
Question
Hydrogen atom emits blue light when it jumps from n = 4 energy level to the n = 2 energy level. Which colour of light would the atom emit when it jumps from the n = 5 level to the n = 2 level?
Question 13
Question
The electromagnetic theory of light was developed by
Answer

Max Planck

Maxwall

Newton

Huygens
Question 14
Question
The concept of quantum nature of light has emerged in an attempt to explain
Question 15
Question
The electron in the innermost orbit of an atom has _____ velocity.
Question 16
Question
Einstein’s photoelectric equation was experimentally verified by
Answer

Millikan

Rutherford

Einstein

Fermi

all the above
Question 17
Question
A photon of energy 8 eV is incident on a metal surface of threshold frequency 1.6 1015 Hz. The K.E of the photoelectrons emitted (in eV) (Take h = 6 10–34 Js)
Question 18
Question
TV waves have a wavelength range of 110 metre. This frequency range in MHz is
Answer

3 – 3000

300 – 3000

3 – 30

30 – 300
Question 19
Question
. An electron and a proton have the same deBroglie wavelength. Then the kinetic energy of the electron is
Question 20
Question
Whenever a hydrogen atom emits a photon in the Balmer series
Answer

It may emit another photon in the Balmer series

It must emit another photon in the Lyman series

It may emit another photon in the Paschen series

It need not emit any more photon
Question 21
Question
The de Broglie wavelength of an electron in the first Bohr orbit is
Answer

equal to the circumference of the first orbit

equal to twice the circumference of the first orbit

equal to half the circumference of the first orbit

equal to one fourth the circumference of the first orbit