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

The shortest wavelength of the Brackett series of a hydrogen like atom of atomic number Z is same as the shortest wavelength of the Balmer series of hydrogen atom, then the value of Z is ______.

A charged particle is accelerated through a potential difference of 12 kV and acquires a speed of 10⁶ ms^-1. It is projected perpendicularly into the magnetic field of strength 0.2 T. The radius of the circle described is ______ cm.

A charge Q is moving `vec"dl"` distance in the magnetic field `vec"B"`. Find the value of work done by `vec"B"`.

Protons and singly ionized atoms of U²³⁵ and U²³⁸ are passed in turn (which means one after the other and not at the same time) through a velocity selector and then enter a uniform magnetic field. The protons describe semicircles of radius 10 mm. The separation between the ions of U²³⁵ and U²³⁸ after describing the semicircle is given by ______.

One mole of gas expands obeying the relation as shown in the P-V diagram. The maximum temperature in this process is equal to ______.

Choose the correct option from the following options given below:

An alpha nucleus of energy `1/2`mv² bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to ______.

1. v²
2. `1/"m"`
3. `1/"v"^2`
4. `1/"Ze"`

In the Rutherford experiment, α-particles are scattered from a nucleus as shown. Out of the four paths, which path is not possible? 

The energy band gap of semiconducting material to produce violet (wavelength = 4000 Å).

LED is ______ eV. (Round off to the nearest integer)

When a diode is forward biased, it has a voltage drop of 0.5 V. The safe limit of current through the diode is 10 mA. If a battery of emf 1.5 V is used in the circuit, the value of minimum resistance to be connected in series with the diode so that the current does not exceed the safe limit is ______.

A charged particle of charge q and mass m is projected in a region that contains an electric and magnetic field as shown in the figure with velocity V at an angle of 45° with x-direction. If V = `sqrt((qE)/m)`, then net deviation in particle motion will be (neglect the effect of gravity) in a clockwise direction approx ______ °.

A person moved from A to B on a circular path as shown in figure. If the distance travelled by him is 60 m, then the magnitude of displacement would be: (Given cos135° = - 0.7)

A car covers the first half of the distance between two places at 40 km/h and other half at 60 km/h. The average speed of the car is ______.

Two bodies of mass 1 kg and 3 kg have position vectors `hati + 2hatj + hatk` and `-3hati - 2hatj + hatk` respectively. The magnitude of position vector of centre of mass of this system will be similar to the magnitude of vector ______.

A planet revolving in an elliptical orbit has:

1. a constant velocity of revolution.
2. has the least velocity when it is nearest to the sun.
3. its areal velocity is directly proportional to its velocity.
4. areal velocity is inversely proportional to its velocity.
5. to follow a trajectory such that the areal velocity is constant.

Choose the correct answer from the options given below:

lf the angular momentum of a planet of mass m, moving around the Sun in a circular orbit is L, about the center of the Sun, and its areal velocity is ______.

When a particle executes Simple Harmonic Motion, the nature of the graph of velocity as a function of displacement will be ______.

A particle performs simple harmonic motion with a period of 2 seconds. The time taken by the particle to cover a displacement equal to half of its amplitude from the mean position is `1/a` s. The value of 'a' to the nearest integer is ______.

Four identical particles of equal masses 1 kg made to move along the circumference of a circle of radius 1 m under the action of their own mutual gravitational attraction. The speed of each particle will be ______.

The radiation corresponding to the 3 → 2 transition of a hydrogen atom falls on a gold surface to generate photoelectrons. These electrons are passed through a magnetic field of 5 × 10^-4 T. Assume that the radius of the largest circular path followed by these electrons is 7 mm, and the work function of the metal is ______.

(Mass of electron = 9.1 × 10^-31 kg)