Modern Physics PYQ — Page 12

The half life of a radium is about 1600 years. Of $100 \mathrm{~g}$ of radium existing now 25 g will remain unchanged after :-

The output of OR gate is 1 :

In a $p-n$ junction photocell, the value of the photo electromotive force by monochromatic light is proportional to:

Energy $E$ of a hydrogen atom with principal quantum number $n$ is given by $E=\frac{-13.6}{n^2} \mathrm{eV}$. The energy of a photon ejected when the electron jumps for $n=3$ state $n=2$ state of hydrogen is approximately

A nucleus represented by the symbol ${ }_{\mathrm{A}}^{\mathrm{A}} \mathrm{X}$ has:

On the diodes shown in the following diagrams, which one is reverse biased:

$M_P$ denotes the mass of a proton and $M_n$ that a neutron. A given nucleus, of binding energy $\mathrm{B}$, contains $Z$ protons and $N$ neutrons. The mass $M(N, Z)$ of the nucleus is given by $(c$ is the velocity of light):

According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectron ejected and the frequency of incident radiation is:

If a nuclear fusion process the masses of the fusing nuclei be $m_1$ and $m_2$ and the mass of the resultant nucleus be $m_3$, then:

In semiconductors at a room temperature:

The Bohr model of atoms:

The peak voltage in the output of a halfwave diode rectifier fed with a sinusiodal signal without filter is $10 \mathrm{~V}$. The d.c. component of the output voltage is:

If a full wave rectifier circuit is operating from $50 \mathrm{~Hz}$ mains, the fundamental frequency in the ripple will be:

Barrier potential of a $p-n$ junction diode does not depend on:

Following diagram performs the logic function of: 

The volume occupied by an atom is greater than the volume of the nucleus by a factor of about:

A sample of radioactive element has a mass of $10 \mathrm{~g}$ at an instant $t=0$. The approximate mass of this element in the sample after two mean lives is:

The mass number of a nucleus is:

Reverse bias applied to a junction diode

The mass of proton is $1.0073 u$ and that of neutron is $1.0087 u(u=$ atomic mass unit). The binding energy of ${ }_2^4 \mathrm{He}$ is: (Given helium nucleus mass $\approx 4.0015$ u)

A photoelectric cell is illuminated by a point source of light $1 \mathrm{~m}$ away. When the source is shifted to $2 \mathrm{~m}$ then:

In which of the following systems will the radius of the first orbit $(n=1)$ be minimum?

Solar energy is mainly caused due to:

J.J. Thomson's cathode ray tube experiment demonstrated that: