List of top Physics Questions

Photodiode is a device

The x and y coordinates of the particle at any time are $x = 5t - 2t^2$ and $y = 10t$ respectively, where $x$ and $y$ are in meters and t in seconds. The acceleration of the particle at $t = 2s$ is :

The photoelectric threshold wavelength of silver is $3250 \times 10^{-10}m$. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength $2536 \times 10^{-10} m $ is (Given $ h = 4.14 \times 10^{-15} eVs$ and $c = 3 \times 10^8 \, ms^{-1}$)

Suppose the charge of a proton and an electron differ slightly. One of them is $- e$, the other is ($e + \Delta e $). If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance $d$ (much greater than atomic size) apart is zero, then $\Delta e$ is of the order of [Given mass of hydrogen $m_h = 1.67 \times 10^{-27} \, kg$]

The ratio of resolving powers of an optical microscope for two wavelengths $\lambda_1 = 4000 \mathring A$ and $\lambda_2 = 6000 \mathring A$ is :

Radioactive material $'A'$ has decay constant $' 8 \lambda '$ and material $'B' $ has decay constant $'\lambda'$ Initially they have same number of nuclei. After what time, the ration of number of nuclei of material of material $'B' $ to that $'A'$ will be $\frac{1}{e} ?$

Two Polaroids $P_1 $ and $P_2$ are placed with their axis perpendicular to each other. Unpolarised light $I_0$ is incident on $P_1$. A third polaroid $P_3$ is kept in between $P_1$ and $P_2$ such that is axis makes an angle 45$^{\circ}$ with that of $P_1$ .The intensity of transmitted light through $P_2$ is : -

The observer is moving with velocity $v_0$ towards the stationary source of sound and then after crossing moves away from the source with velocity $v_0$. Assume that the medium through which the sound waves travel is at rest. If $V$ is the velocity of sound and $n$ is the frequency emitted by the source then the difference between apparent frequencies heard by the observer is

Two discs of same moment of inertia rotating about their regular axis passing through centre and perpendicular to the plane of disc with angular velocities $\omega_1$ and $\omega_2$ . They are brought into contact face to face coinciding the axis of rotation. The expression for loss of energy during this process is:-

There is a uniform electrostatic field in a region. The potential at various points on a small sphere centred at $P$, in the region, is found to vary between the limits $589.0\, V$ to $589.8\, V$. What is the potential at a point on the sphere whose radius vector makes an angle of $60^{\circ}$ with the direction of the field ?

The following observations were taken for determining surface tension T of water by capillary method: diameter of capillary, \(D = 1.25 \times 10^{-2} \, m\)rise of water, \(h = 1.45 \times 10^{-2} m\). Using \(g = 9.80 \, m/s^2\) and the simplified relation \(T = \frac{rhg}{2} \times 10^3 \, N/m\) , the possible error in surface tension is closest to:

Which one of the following consumes least amount of electricity?

A magnetic dipole in a constant magnetic field has :

A magnetic needle of magnetic moment $6.7 \times 10^{-2} \, Am^2$ and moment of inertia $7.5 \times 10^{-6} \, kg \, m^2$ is performing simple harmonic oscillations in a magnetic field of $0.01\, T$. Time taken for $10$ complete oscillations is :

Preeti reached the metro station and found that the escalator was not working. She walked up the stationary escalator in time $t_1$. On other days, if she remains stationary on the moving escalator, then the escalator takes her up in time $t_2$. The time taken by her to walk up on the moving escalator will be

A rope of negligible mass is wound round a hollow cylinder of mass $3 \,kg$ and radius $40 \,cm$. If the rope is pulled with a force of $30 \,N$, then the angular acceleration produced in the cylinder is

The magnetic moment of electron due to orbital motion is proportional to (n = principal quantum number)

A capillary tube of radius $R$ is immersed in water and water rises in it to a height $H$. Mass of water in the capillary tube is $M$. If the radius of the tube is doubled, mass of water that will rise in the capillary tube will now be :

The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature $T$ (Kelvin) and mass $m$, is :

A particle is executing simple harmonic motion with a time period $T$. At time $t = 0$, it is at its position of equilibrium. The kinetic energy - time graph of the particle will look like :

A solid rectangular sheet has two different coefficients of linear expansion $\alpha_{1}$ and $\alpha_{2}$ along its length and breadth respectively. The coefficient of surface expansion is (for $\alpha_{1} t < < 1, \alpha_{2} t < < 1$)

A parallel beam of light is incident on a glass prism in the shape of a quarter cylinder of radius $R \,= \,0.05\, m$ and refractive index n = $1.5$ placed on a horizontal table as shown in the figure. Beyond the cylinder, a patch of light is found whose nearest distance $x$ from the cylinder is

An ice-berg of density \(900\ kgm^{-3}\) is floating in water of density \(1000\  kgm^{-3}\). The percentage of volume of ice-berg outside the water is