When an electron jumps from the orbit n = 2 to n = 4, then wavelength of the radiations absorbed will be _________ (R is Rydberg’s constant)

In a pure semiconductor crystal, if current flows due to breakage of crystal bonds, then what is the semiconductor called?

The optical element used to split a poly-chromatic light into its constituent component colors is called:

In a coil current changes from $4A$ to $2A$ in $0.05$ sec, if induced e.m.f. is $8$ volt then self-inductance of the coil is:

Keeping voltage constant, if more lamps are put into a series circuit, the overall current in the circuit:

How are charge carriers produced in intrinsic semiconductors?

On what application does the speedometer works?

The work function of Cesium is 2.27eV. The cut-off voltage which stops the emission of electrons from a cesium cathode irradiated with light of 600nm wavelength is:

Calculate the Bohr radius of 3rd orbit of Be³⁺.

Which of the following force does not follow the inverse square law?

Which of the following options is correctly depicting the formula of power?

Linearly polarized wave:

The photoelectric cut-off voltage in a certain experiment is 1.5 V. What is the maximum kinetic energy of photoelectrons emitted?

The electric field at a point is:

Visible spectrum lies between:

The work function of tungsten is $4.50\mathrm{eV}$. The wavelength of the fastest electron emitted when light whose photon energy is $5.50\mathrm{eV}$ falls on a tungsten surface, is?

The intensity ratio of two waves is $1:9$. The ratio of their amplitudes is:

A hollow metal sphere of radius $R$ is uniformly charged. The electric field due to the sphere at a distance $r$ from the centre:

The magnetic field at a distance $\mathrm{r}$ from a long wire carrying a current $i$ is $0.4\mathrm{T}$. The magnetic field at a distance $2\mathrm{r}$ is:

Two thin equiconvex lenses, each of focal length $0.2$ m, are placed coaxially with their optic centres $0.5$ m apart. What is the focal length of the combination?

The equivalent resistance between A and B is _________

Which of the following electromagnetic wave is used for thermal imaging?

A dielectric slab of thickness $1.0cm$ and dielectric constant 5 is placed between the plates of a parallel plate capacitor of plate area $0.01m^2$ and separation $2.0cm$. Calculate the change in capacity on introduction of dielectric.  

A short bar magnet placed with its axis at ${30}^{\circ }$ with a uniform external magnetic field of $0.25\mathrm{T}$ experiences a torque of magnitude equal to $4.5\times {10}^{-2}\mathrm{J}$. What is the magnitude of magnetic moment of the magnet?

Infrared radiation was discovered in 1800 by ______

The kinetic energy of the fastest moving photo electron from a metal of work function 2.8 eV is 2 eV. If the frequency of light is doubled, then find the maximum kinetic energy of photo electron.

Calculate the wavelength of radiation emitted when He+ makes a transition from the state n = 4 to the state n = 3.

If the electrical conductivity of a semiconductor increases when electromagnetic radiation of a wavelength shorter than $2480$ nm is incident on it. What is the bandgap (in eV) for the semiconductor? 

In electromagnetic induction, the induced e.m.f. in a coil is independent of:

A convex lens of focal length 50 cm and a concave lens of focal length 25 cm are placed in contact with each other. Then the equivalent focal length of the combination will be:

Consider the following statements:

1. The shorter length of the potentiometer wire is preferred.
2. Copper wire is used in potentiometers.
3. The electric field inside the potentiometer is variable.
4. If the length of the wire is halved, the position of zero deflection in a potentiometer occurs at a longer length.

Which of the following statement is incorrect?

Identify the logic gate carried out by the following circuit.

___________ are those which gets strongly magnetised when placed in an external magnetic field.

The electrostatic force of repulsion between two positively charged ions carrying equal charge is $3.7\times {10}^{-9}\mathrm{N}$, when they are separated by a distance of $5$Å. How many electrons are missing from each ion?

The phase difference between the electric field and the magnetic field in the electromagnetic wave is:

The output of a NOR gate is high if ______.

How many coulombs of charge do $25\times {10}^{31}$ electrons possess?

A thin wire loop carrying a current $I$ is placed in a uniform magnetic field $B$ pointing out of the plane of the coil as shown in the figure. The loop will tend to _____________.

A nucleus with $\mathrm{Z}=92$ emits the following in a sequence $\alpha ,\alpha ,{\beta }^{-},{\beta }^{-},\alpha ,\alpha ,\alpha ,\alpha ,{\beta }^{-},{\beta }^{-},\alpha ,{\beta }^{+},{\beta }^{+},\alpha$. The $\mathrm{Z}$ of the resulting nucleus is:

Two coils of self-inductance $L_1$ and $L_2$ are placed closer to each other so that total flux in one coil is completely linked with others. If M is mutual inductance between them, then: