JEE Main entrance exam Question Bank Solutions for Physics (JEE Main)

The half-value thickness of an absorber is defined as the thickness that will reduce exponentially the intensity of a beam of particles by a factor of 2. The half-value thickness in (µm) for lead assuming X-ray beam of wavelength 20 pm, µ = 50 cm^-1 for X-rays in lead at wavelength λ = 20 pm, is ______ µm.

A smooth sphere of radius R and mass M is placed on the smooth horizontal floor. Another smooth particle of mass m is placed on the sphere and a horizontal force F is applied on the sphere as shown. If the particle does not slip on the sphere then the value of force F is ______.

An expansion process on a diatomic ideal gas (C_v = 5/2 R), has a linear path between the initial and final coordinates on a pV diagram. The coordinates of the initial state are: the pressure is 300 kPa, the volume is 0.08 m³ and the temperature is 390 K. The final pressure is 90 kPa and the final temperature s 320 K. The change in the internal energy of the gas, in SI units, is closest to:

A gas is compressed at a constant pressure of 50 N/m² from a volume of 10 m³ to a volume of 4 m³. Energy of 100 J is then added to the gas by heating. Its internal energy is ______.

Two blocks A and B of masses m and 2 m, respectively, are held at rest such that the spring is in natural length. Find out the accelerations of both the blocks just after release.

The masses of 10 kg and 20 kg, respectively, are connected by massless spring as shown in the figure. A force of 200 N acts on the 20 kg mass. At the instant shown, the 10 kg mass has acceleration of 12 m/s². What is the acceleration of 20 kg mass?

(g = 10 m/s²)

In uranium (Z = 92) the K absorption edge is 0.107 Å and the K_α line is 0.126 Å, and the wavelength of the L absorption edge is ______.

The velocity at which the mass of a particle becomes twice its rest mass will be ______.

Given below in the left column are different modes of communication using the kinds of waves given in the right column. 

From the options given below, find the most appropriate match between entries in the left and the right column.

A force F is applied to the initially stationary cart. The variation of force with time is shown in the figure. The speed of the cart at t = 5 sec is ______.

Which is the correct ascending order of wavelengths?

Photons of an electromagnetic radiation has an energy 11 keV each. To which region of electromagnetic spectrum does it belong? 

An electron in H-atom makes a transition from n = 3 to n = 1. The recoil momentum of the H-atom will be ______.

Find the ratio of energies of photons produced due to transition of an election of hydrogen atom from its (i) second permitted energy level to the first level. and (ii) the highest permitted energy level to the first permitted level.

A hydrogen atom in its first excited state absorbs a photon of energy x × 10^-2 eV and exited to a higher energy state where the potential energy of electron is -1.08 eV. The value of x is ______.

In Bohr's atomic model of hydrogen, let K. P and E are the kinetic energy, potential energy and total energy of the electron respectively. Choose the correct option when the electron undergoes transitions to a higher level:

According to Bohr atom model, in which of the following transitions will the frequency be maximum?

The electron in a hydrogen atom first jumps from the third excited state to the second excited state and subsequently to the first excited state. The ratio of the respective wavelengths, λ₁/λ₂, of the photons emitted in this process is ______. 

The energy required to remove the electron from a singly ionized Helium atom is 2.2 times the energy required to remove an electron from Helium atom. The total energy required to ionize the Helium atom completely is ______. 

Orbits of a particle moving in a circle are such that the perimeter of the orbit equals an integer number of de-Broglie wavelengths of the particle. For a charged particle moving in a plane perpendicular to a magnetic field, the radius of the n^th orbital will therefore be proportional to: