List of top Physics Questions

An astronomical telescope in normal adjustment has magnifying power \(5\) for distant objects. The separation between the objective and the eyepiece is \(36\) cm. The focal lengths of the objective and the eyepiece are respectively

Two coherent monochromatic light beams of intensities \(I\) and \(4I\) are superposed. What are the maximum and minimum possible intensities in the resulting beam?

A double convex lens is made of a certain material. The refractive index of the material of the lens is \(1.55\) for violet rays and \(1.50\) for red rays. If the focal length of the lens is \(20\) cm for violet rays, then the focal length of the lens for red rays is

A parallel plate capacitor with circular plates of radius $R$ is being charged as shown in the figure. Let $B(r)$ be the induced magnetic field at a distance $r$ from the central axis between the plates. Assuming $d \ll R$, the ratio $\frac{B(2d)}{B(d)}$, while charging, is

A laser beam of wavelength $1\text{ }\mu\text{m}$ is split and sent into two vacuum cavities of equal length $L$ as shown in the figure. A detector can register an interference signal only if the phase difference between the returning beams is at least $5 \times 10^{-11}\text{ rad}$. A certain physical effect changes the length of cavity 2 by an amount $\Delta L$ such that $\Delta L / L \approx 10^{-21}$. The minimum cavity length (in km) needed for measuring this physical effect is approximately

Two point bodies of masses $m$ and $3m$ are connected by a massless spring of spring constant $k = m\omega_0^2$ and kept on a frictionless horizontal surface. The spring is extended by a small distance $l$ over its natural length at time $t = 0$ and then released so that the masses execute simple harmonic motion. The maximum speed of the particle with mass $m$ is given by

The critical electric field required to produce electron-positron pairs depends on the physical constants $h$, $c$, $m_e$ and $e$. Use dimensional analysis and assume that the dimensionless coefficient is of order one. The magnitude of the critical electric field, in SI units, is of the order

The electron in the hydrogen atom is in the third excited state. Its potential energy (in eV) is

All the capacitors in a given circuit are initially fully charged with all switches open. At a later time $t$, all the switches are simultaneously closed. The current flowing through the circuit at that instant is given by

Two protons are separated by a distance of 1 nanometer. The magnitudes of gravitational, electromagnetic and strong nuclear forces between them are denoted by $F_G$, $F_E$ and $F_S$ respectively. Select the correct option.

A sphere is given an initial push so that it starts rolling (without slipping) up an inclined plane. During its climb

An incandescent lamp of wattage $W$ is filled with argon gas and has a tungsten filament. The collision frequency of evaporated tungsten atoms with the argon atoms is found to be proportional to $W^\alpha$. The most reasonable value of $\alpha$ is

One mole of a monatomic ideal gas undergoes a transformation from an initial state with temperature $290\text{ K}$ and volume $30\text{ litres}$ to a final state with temperature $310\text{ K}$ and volume $16\text{ litres}$. On the pressure–volume ($P - V$) diagram, this process is represented by a straight line path. The magnitude of the work done (in joules) during this process is close to

A sphere made of a material with density $12\text{ kg}\cdot\text{m}^{-3}$ and weighing $100\text{ N}$ in vacuum is immersed in a container of gas. Its weight in gas is $85\text{ N}$. The density of the gas in $\text{kg}\cdot\text{m}^{-3}$ is closest to

An infinitely long straight wire with uniform line charge density $\lambda$ lies at a perpendicular distance $d$ from a point O. The total electric flux through the surface of a sphere of radius $R \gt d$ centred at O, is

Two wave pulses, one rectangular and other triangular, approach each other as shown in the figure below.

They overlap at the point P at time $t$. The diagram best representing the appearance of the wave pulses at a time $t' \gt t$ is

Physicist Luis Alvarez and his collaborators hypothesised that the extinction of dinosaurs was due to the impact of an asteroid with the Earth. They estimated the mass and the radius of the asteroid to be about $2 \times 10^{15}\text{ kg}$ and $10\text{ km}$ respectively. Take the mass of the Earth to be $6 \times 10^{24}\text{ kg}$. The gravitational acceleration (in SI units) of the Earth due to the asteroid just before the impact would be of the order

Ice on land mass melting into ocean, due to global warming, is estimated to be around $1.3 \times 10^{15}\text{ kg}$ per year. The density of sea water is $1025\text{ kg}\cdot\text{m}^{-3}$. Assuming that the melting rate of ice remains constant and the effective surface area covered by the oceans is $3.6 \times 10^{14}\text{ m}^2$, the estimated average rise in sea level (in m) in the next 75 years will be closest to

A spherical glass bottle having negligible wall thickness is placed in air. When the bottle is completely filled with water, its focal length is $f$. If the water is replaced by another transparent liquid of higher refractive index, then the focal length changes to $f'$. Then

Let $A$ be the mass number, $Z$ be the atomic number and $N$ be the neutron number of a nucleus. Then the statement which is always true, is

The angular speed of the Earth’s rotation is $7.3 \times 10^{-5}\text{ rad}\cdot\text{s}^{-1}$. Take the radius of the Earth at the equator to be $6400\text{ km}$. Then the ratio ($a_c / g$) of the magnitude of the centripetal acceleration $a_c$ at a point on the equator to $g$, is of the order

Among the following, the waves responsible for energy transfer in vacuum are

An electromagnetic wave travels from vacuum into a non-magnetic dielectric medium with permittivity $\epsilon = 4\epsilon_0$. If the ratio ($E_0 / B_0$) of the electric field amplitude $E_0$ to the magnetic field amplitude $B_0$ in vacuum is equal to the speed of light $c$, then the corresponding ratio in the given medium is

A ray of light MN is incident normally on the face corresponding with side AB of a prism with an isosceles right-angled triangular base ABC. Trace the path of the ray as it passes through the prism when the refractive index of the prism material is \( \sqrt{2} \), and \( \sqrt{3} \).