NEET UG 2020 — Modern Physics

In Bohrs model, the radius of nth orbit is proportional to

An intrinsic semiconductor is converted into $n$-type extrinsic semiconductor by doping it with:-

The total energy of an electron in the ${n}^{\text{th }}$ stationary orbit of the hydrogen atom can be obtained by

Which of the following gate is called universal gate?

For the logic circuit shown, the truth table is: 

The de-Broglie wavelength of an electron moving with kinetic energy of $144\mathrm{eV}$ is nearly

What happens to the mass number and atomic number of an element when it emits $\gamma$-radiation

The increase in the width of the depletion region in a p-n junction diode is due to:

Light of frequency $1.5$ times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled?

The half life of radioactive sample undergoing $\alpha$-decay is $1.4\times {10}^{17}s.$ If the number of nuclei in the sample is $2.0\times {10}^{21},$ the activity of the sample is nearly:

Out of the following which one is a forward biased diode?

When a uranium isotope $U92235$ is bombarded with a neutron, it generates $\mathrm{Kr}3689$, three neutrons and:

The energy equivalent of $0.5g$ of a substance is:

An electron is accelerated from rest through a potential difference of $V$ volt. If the de Broglie wavelength of the electron is $1.227\times {10}^{–2} \mathrm{nm}$, the potential difference is:

The solids which have the negative temperature coefficient of resistance are:

For which one of the following, Bohr model is not valid?