Modern Physics PYQ — Page 27

If the kinetic energy of a free electron doubles. Its deBroglie wavelength changes by the factor

A photocell is illuminated by a small bright source placed $1 \mathrm{~m}$ away. When the same source of light is placed $\frac{1}{2} \mathrm{~m}$ away, the number of electrons emitted by photo cathode would

If radius of ${ }_{13}^{27} \mathrm{Al}$ nucleus is estimated to be $3.6$ Fermi then the radius ${ }_{52}^{125} \mathrm{Te}$ nucleus be nearly

In a full wave rectifier circuit operating from $50 \mathrm{~Hz}$ mains frequency, the fundamental frequency in the ripple would be

The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy ? 

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480 \mathrm{~nm}$ is incident on it. The band gap in (eV) for the semiconductor is

A nuclear transformation is denoted by $X(n, \alpha){ }_3^7 \mathrm{Li}$. Which of the following is the nucleus of element $X$ ?

The manifestation of band structure in solids is due to

The binding energy per nucleon of deuteron $\left({ }_1^2 \mathrm{H}\right)$ and helium nucleus $\left({ }_2^4 \mathrm{He}\right)$ is $1.1 \mathrm{MeV}$ and $7 \mathrm{MeV}$ respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is

The work function of a substance is $4.0 \mathrm{eV}$. Then longest wavelength of light that can cause photoelectron emission from this substance approximately

According to EInstein's photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal $\mathrm{V}_{\mathrm{s}}$ the frequency, of the incident radiation gives straight line whose slope

When p-n junction diode is forward biased

A radiation of energy $E$ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is

A nucleus disintegrates into two nuclear parts which have their velocities in the ratio $2: 1$. The ratio of their nuclear sizes will be

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

The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the

Two identical photocathodes receive light of frequencies $\mathrm{f}_1$ and $\mathrm{f}_2$. If the velocities of the photo electrons (of mass $\mathrm{m}$ ) coming out are respectively $\mathrm{v}_1$ and $\mathrm{v}_2$, then

In the middle of the depletion layer of a reverse biased p-n junction, the

If the binding energy of the electron in a hydrogen atom is $13.6 \mathrm{eV}$, the energy required to remove the electron from the first excited state of $\mathrm{Li}^{++}$is

Which of the following atoms has the lowest ionization potential?

The wavelengths involved in the spectrum of deuterium $\left({ }_1^2 \mathrm{D}\right)$ are slightly different from that of hydrogen spectrum, because

When a $U^{238}$ nucleus originally at rest, decays by emitting an alpha particle having a speed ' $u$ ', the recoil speed of the residual nucleus is

At absolute zero, Si acts as

The energy band gap is maximum in