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

The value of tension in a long thin metal wire has been changed from T₁ to T₂. The lengths of the metal wire at two different values of tension T₁ and T₂ are l₁ and l₂ respectively. The actual length of the metal wire is ______.

A body having specific charge 8 µC/g is resting on a frictionless plane at a distance 10 cm from the wall (as shown in the figure). It starts moving towards the wall when a uniform electric field of 100 V/m is applied horizontally toward the wall. If the collision of the body with the wall is perfectly elastic, then the time period of the motion will be ______ s.

The stopping potential in the context of photoelectric effect depends on the following property of incident electromagnetic radiation ______.

The volume V of an enclosure contains a mixture of three gases, 16 g of oxygen, 28 g of nitrogen and 44 g of carbon dioxide at absolute temperature T. Consider R as universal gas constant. The pressure of the mixture of gases is ______.

The first three spectral lines of H-atom in the Balmer series are given λ₁, λ₂, λ₃ considering the Bohr atomic model, the wavelengths of the first and third spectral lines `(lambda_1/lambda_3)` are related by a factor of approximately 'x' × 10^–1. The value of x, to the nearest integer, is ______.

In a photoelectric experiment, ultraviolet light of wavelength 280 nm is used with a lithium cathode having work function Φ = 2.5 eV. If the wavelength of incident light is switched to 400 nm, find out the change in the stopping potential.

(h = 6.63 × 10^-34 Js, c = 3 × 10⁸ ms^-1)

When radiation of wavelength λ is used to illuminate a metallic surface, the stopping potential is V. When the same surface is illuminated with radiation of wavelength 3λ, the stopping potential is `"V"/4`. If the threshold wavelength for the metallic surface is nλ. then value of n will be ______.

A light is entering from one medium refractive index `("RI" =5/3)` to another medium at an angle 30°. The angle of refraction for other medium is sin^-1 `(5/6)`. then the increase in angle of incidence is ______ such that the ray of light reflected back into the same medium.

The velocities of a particle in SHM at positions x₁ and x₂ are v₁ and v₂ respectively, its time period will be ______.

Photoelectrons are observed to just emit out of a material surface when the light of 620 nm falls on it with the intensity of 100 W m^-2. If the light of wavelength 400 nm is incident on the same material with an intensity of 1 W m^-2, what would be the minimum reverse potential needed to stop the outflow of the electrons?

The radiation emitted, when an electron jumps from n = 3 to n = 2 orbit is a hydrogen atom, falls on a metal to produce photoelectron. The electrons from the metal surface with maximum kinetic energy are made to move perpendicular to a magnetic field of `1/320`T in a radius of 10^-3m. Find the 320 work function of metal:

A steel wire having a radius of 2.0 mm, carrying a load of 4 kg, is hanging from a ceiling. Given that g = 3.1πms^-2, what will be the tensile stress that would be developed in the wire?

A container consist of hemispherical shell of radius 'r ' and cylindrical shell of height 'h' radius of same material and thickness. The maximum value h/r so that container remain stable equilibrium in the position shown (neglect friction) is ______.

A weightless rigid rod with a small iron bob at the end is hinged at point A to the wall so that it can rotate in all directions. The rod is kept in the horizontal position by a vertical inextensible string of length 20 cm, fixed at its midpoint. The bob is displaced slightly, perpendicular to the plane of the rod and string. The period of small oscillations of the system in the form `(pix)/10` is ______ sec. and the value of x is ______.

(g = 10 m/s²)

The wavelength of light incident on a metal surface is reduced from 300 nm to 200 nm (both are less than threshold wavelength). What is the change in the stopping potential for photoelectrons emitted from the surface will be ______ V. (Take h = 6.6 × 10^-34 J-s)

When ultraviolet light of wavelength 100 nm is incident upon a sample of silver metal, a potential difference of 7.7 volt is required to stop the photoelectrons from reaching the collector plate. The potential required to stop photo electrons when light of wavelength 200 nm is incident upon silver is ______.

A coil is placed in a time varying magnetic field. If the number of turns in the coil were to be halved and the radius of wire doubled, the electrical power dissipated due to the current induced in the coil would be: (Assume the coil to be short circuited.)

A circular coil of 1000 turns each with area 1 m² is rotated about its vertical diameter at the rate of one revolution per second in a uniform horizontal magnetic field of 0.07T. The maximum voltage generation will be ______ V.

The maximum kinetic energy of the photoelectrons ejected will be ______ eV when the light of wavelength 350 nm is incident on a cesium surface. The work function of cesium = 1.9 eV.

Which of the following is used in optical fibres?