Class 12th

Concentric metallic hollow spheres of radii   $R$ and $4R$    hold charges $Q_1$ and ${\mathrm{Q}}_2$  respectively. Given that surface charge densities of the concentric spheres are equal, the potential difference $V\left(R\right)-V\left(4R\right)$  is:

Two sources of light emit $X$  - rays of wavelength   $1\mathrm{n}\mathrm{m}$ and visible light of wavelength $500\mathrm{n}\mathrm{m}$   , respectively. Both the sources emit light of the same power $200\mathrm{W}$   . The ratio of the number density of photons of $X$  - rays to the number density of photons of the visible light of the given wavelengths is:

Which of the following will NOT be observed when a multimeter (operating in resistance measuring mode) probes connected across a component, are just reversed?

Given figure shows few data points in a photo electric effect experiment for a certain metal. The minimum energy for ejection of electron from its surface is: (Plancks constant ${}^{}$ )

On the $$ $x$ -axis and at a distance $x$ $$ from the origin, the gravitational field due to a mass distribution is given by $\frac{Ax}{{\left(x^2+a^2\right)}^{3/2}}$ $\frac{}{{\left({}^{}{}^{}\right)}^{}}$ in the $x$ $$ -direction. The magnitude of gravitational potential on the $x$ $$ -axis at a distance $x$ $$ , taking its value to be zero at infinity is:

Hydrogen ion and singly ionized helium atom are accelerated, from rest, through the same potential difference. The ratio of final speeds of hydrogen and helium ions is close to:

The electric field of a plane electromagnetic wave propagating along the $x$  direction in vacuum is $\vec{E}=E_0\hat{j}\mathrm{c}\mathrm{o}\mathrm{s}(\omega t-kx)$   . The magnetic field $\vec{B}$ , at the moment   $t=0$ is:

The Boolean expression Y = A'BC + AC can be realised with which of the following gate configurations.
A. One 3-input AND gate, 3 NOT gates and one 2-input OR gate, One 2 -input AND gate,
B. One 3-input AND gate, 1 NOT gate, One 2-input NOR gate and one 2-input OR gate
C. 3-input OR gate, 3 NOT gates and one 2-input AND gate
Choose the correct answer from the options given below