Physics

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?

The work function for aluminium is 4.125 eV. The cut off wavelength for photoelectric effect for Aluminium is

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

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

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

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

When Boron 5B10 is bombarded by neutron,  particles are emitted. The resulting nucleus has mass number

Tracer techniques make use of

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?

The unit of Planck’s constant is

Mean life of a radioactive element is one year. Then its half life is (years)

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?

The electromagnetic theory of light was developed by

The concept of quantum nature of light has emerged in an attempt to explain

The electron in the innermost orbit of an atom has _____ velocity.

Einstein’s photoelectric equation was experimentally verified by

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)

TV waves have a wavelength range of 1-10 metre. This frequency range in MHz is

. An electron and a proton have the same de-Broglie wavelength. Then the kinetic energy of the electron is

Whenever a hydrogen atom emits a photon in the Balmer series

The de Broglie wavelength of an electron in the first Bohr orbit is