Test on Modern Physics for JEE Main 2017 for JEE & BITSAT Exams

Question 1

Suppose, the electron in a hydrogen atom makes transition from n = 3 to n = 2 in 10^–8 s. The order of the torque acting on the electron in this period, using the relation between torque and angular momentum as discussed in the chapter on rotational mechanics is -

Question 2

In hydrogen atom, the radius of n^th Bohr orbit is r_n. The graph between log (r_n/r₁) and log n will be -

Question 3

The magnetic field at the centre of a hydrogen atom due to the motion of the electron in the first Bohr orbit is B. The magnetic field at the centre due to the motion of the electron in the second Bohr orbit will be -

Question 4

An electron of energy 10.8 eV undergoes an inelastic collision with a hydrogen atom in its ground state. Then (assuming m_H >> m_e, neglecting recoil of atom) -

Question 5

Three photons coming from excited-hydrogen sample an picked up. Their energies are 12.1 eV, 10.2 eV and 1.9 eV. These photons must come from

Question 6

The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function (in eV) of the metal is : (hc = 1240 eV.nm)

Question 7

The average life time of an excited state of hydrogen is of the order of 10^–8 s. The number of orbits an electron makes, when it is in the state n = 2 (before it starts a transition to a lower state) will be (take T₀ to be time period of revolution in ground state in s.)

Question 8

The figure indicates the energy level diagram of an atom and the origin of six spectral lines in emission (e.g. line no. 5 arises from the transition from level B to A). Which of the following spectral lines will also occur in the absorption spectrum ?

Question 9

Proton and α-particles have the same de-Broglie wavelength. What is the same for both of them -

Question 10

A proton accelerated through a potential difference of 100V, has de-Broglie wavelength λ₀. The de-Broglie wavelength of an α-particle, accelerated through 800V is-