List of top Physics Questions

In a photoelectric experiment the incident photons have frequency \( \frac{3}{2} \nu \), where \( \nu \) is the threshold frequency of the material. What is the kinetic energy of the emitted electrons?
If the energy released in the fission of one uranium nucleus is 200 MeV, then the number of fissions per second required to produce 20 MW is:
If the half-life of a radioactive material is 5 days, then the ratio of the number of atoms disintegrated in 10 and 15 days is:
If the relative error in the determination of area of a body is 0.08, then the percentage error in the determination of its volume is
The weight of a body at a height of 3$R_E$ from the surface of the earth is 90 N, where $R_E$ is the radius of the earth. The weight of the same body at a height of $R_E$ from the surface of the earth is:
The blades of a windmill generating electrical energy sweep out an area of 20 m$^2$. If the efficiency of the windmill is 25% and wind speed is 36 kmph, then the electrical power generated is (Density of air = 1.2 kg m$^{-3}$):
A resistor of resistance 160 $\Omega$, an inductor of 280 mH, and a capacitor are connected in series to an AC source of 80 V, 50 Hz. If the circuit is in resonance, the potential difference across the capacitor is:
An observer moves towards a source at rest with a speed of 25% of the speed of sound in air. If the frequency of the sound emitted by the source is 200 Hz, then the frequency of sound heard by the observer is:
A convex lens produces clear images when placed at two positions between an object and a screen that are 1 m apart. If the distance between the two positions of the lens at which clear images are formed is 20 cm, the focal length of the lens is:
If the de Broglie wavelength of a proton accelerated through a potential difference $V_1$ is same as the de Broglie wavelength of an alpha particle accelerated through $V_2$, then $V_1 : V_2 = $
The ratio of frequencies of second line of Lyman series and third line of Balmer series of hydrogen atom is:
If a charge of 3 nC is placed at each vertex of a cube of side 3 m, then the electric potential at the centre of the cube is:
Two charged particles enter a uniform magnetic field normally. If the ratio of the specific charges of the two particles is 2:3, then the ratio of the times taken by the two particles to complete one revolution is:
If the mean life of a radioactive sample is 10 minutes, then the time (in minutes) taken for the activity of the radioactive sample to become $\mathrm{e}^{21}$ times its initial activity is
A layer of oil of thickness 5.8 cm is floating on a water layer of thickness 8 cm. If the total apparent depth is 10 cm and the refractive index of water is 3/4, then the refractive index of oil is
10 g of ice at $-20^\circ$C is dropped into a calorimeter of water equivalent 20 g, containing 10 g of water at $20^\circ$C. At equilibrium, the mass of the ice in the mixture is
A Zener diode of breakdown voltage 6 V is connected as shown in the circuit. The power dissipated in the Zener diode is
A spherical shell of radius 1 m, made of a steel sheet of thickness 5 mm and completely filled with ice at $0^\circ$C is immersed in boiling water. The time taken for the ice to melt completely is (Thermal conductivity of steel = $45~\text{Wm}^{-1}\text{K}^{-1}$ and density of ice is $0.9~\text{g cm}^{-3}$)
The successive frequencies produced by an organ pipe are 330 Hz, 440 Hz and 550 Hz. If the speed of sound in air is 330 m/s then the length of the organ pipe is
The charge on a parallel plate capacitor is 200 μC and its capacitance is 4 μF. If the distance between the plates of the capacitor is 2 mm, then the electric force between the plates of the capacitor is
The Reynolds number and nature of flow of water flowing with a velocity of $10~\text{cm s}^{-1}$ through a pipe of diameter $1.8~\text{cm}$ is (Coefficient of viscosity of water $=10^{-3}~\text{Pa s}$)
A car of mass 1100 kg is moving on a straight rough horizontal surface with a speed of 43.2 kmph. If the coefficient of friction between the surface and the tyres of the car is 0.3, then the shortest distance in which the car can come to rest is (Acceleration due to gravity = $10~\text{m s}^{-2}$)
A body is falling freely under gravity from a certain height from the ground. If the sum of the displacements of the body in the second and third seconds of its motion is 32% of the height from which it is falling, then the speed with which the body hits the ground is (Acceleration due to gravity = $10~\text{m s}^{-2}$)
A body of mass 50 g is projected vertically upwards from the ground. If the kinetic energy of the body at a height of 32 m is 100% more than its potential energy, then the height at which the potential energy of the body becomes 60% of its kinetic energy is
If the time period of an alpha particle rotating in a circular path of radius 2 fermi is 3.14 $\mu$s, then the magnetic field induced at the centre of the circle is nearly