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?
VR
RE
E/V
R/E
The work function for aluminium is 4.125 eV. The cut off wavelength for photoelectric effect for Aluminium is
200 nm
300 nm
150 nm
420 nm
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
n1 = 8, n2 = 2
n1 = 4, n2 = 2
n1 = 6, n2 = 2
n1 = 1, n2 = 2
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
Quadrupled
Doubled
Zero
Halved
A radioactive substance has a half life of four months. Three fourth of the substance will decay in
12 months
4 months
8 months
3 months
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
1
2/3
7/8
5/8
When Boron 5B10 is bombarded by neutron, particles are emitted. The resulting nucleus has mass number
11
6
7
15
Tracer techniques make use of
neutron scattering
electron beams
lasers
radioactive isotopes
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?
2,000
1,000
1,414
707
The unit of Planck’s constant is
Nm
eV
Js–1
Js
Mean life of a radioactive element is one year. Then its half life is (years)
0.5
0.4
0.693
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?
Red
Yellow
Green
Violet
The electromagnetic theory of light was developed by
Max Planck
Maxwall
Newton
Huygens
The concept of quantum nature of light has emerged in an attempt to explain
black – body radiation
photoelectric effect
polarisation of light
interference and diffraction.
The electron in the innermost orbit of an atom has _____ velocity.
mean
zero
highest
lowest
Einstein’s photoelectric equation was experimentally verified by
Millikan
Rutherford
Einstein
Fermi
all the above
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)
2
1.2
1.6
TV waves have a wavelength range of 1-10 metre. This frequency range in MHz is
3 – 3000
300 – 3000
3 – 30
30 – 300
. An electron and a proton have the same de-Broglie wavelength. Then the kinetic energy of the electron is
greater than the kinetic energy of the proton
Infinity
equal to the kinetic energy of the proton
Whenever a hydrogen atom emits a photon in the Balmer series
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
The de Broglie wavelength of an electron in the first Bohr orbit is
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
