List of top Physics Questions

If the energy gap of a semiconductor used for the fabrication of an LED is nearly 1.9 eV, then the color of the light emitted by the LED is
When the receiving antenna is on the ground, the range of a transmitting antenna of height 980 m is (Radius of the earth = 6400 km)
20 kV electrons can produce X-rays with a minimum wavelength of
If the rate of change in electric flux between the plates of a capacitor is \(9\pi \times 10^3 \text{ Vms}^{-1}\), then the displacement current inside the capacitor is
According to a graph drawn between the input and output voltages of a transistor connected in common emitter configuration, the region in which transistor acts as a switch is
A radioactive material of half-life 2.5 hours emits radiation that is 32 times the safe maximum level. The time (in hours) after which the material can be handled safely is
The ratio of wavelengths of second line in Balmer series and the first line in Lyman series of hydrogen atom is
An electric bulb, an open coil inductor, an ac source and a key are all connected in series to form a closed circuit. The key is closed and after some time an iron rod is inserted into the interior of the inductor, then
If the number of uranium nuclei required per hour to produce a power of 64 kW is \(7.2 \times 10^{18}\), then the energy released per fission is
A circular coil of area \(3 \times 10^{-2} \text{ m}^2\), 900 turns and a resistance of 1.8 Ω is placed with its plane perpendicular to a uniform magnetic field of \(3.5 \times 10^{-5}\) T. The current induced in the coil when it is rotated through 180° in half a second is
A square coil of side 10 cm having 200 turns is placed in a uniform magnetic field of 2 T such that the plane of the coil is in the direction of magnetic field. If the current through the coil is 3 mA, then the torque acting on the coil is
The potential difference between points C and D of the electrical circuit shown in the figure is
The length of a potentiometer wire is 2.5 m and its resistance is 8 Ω. A cell of negligible internal resistance and emf of 2.5 V is connected in series with a resistance of 242 Ω in the primary circuit. The potential difference between two points separated by a distance of 20 cm on the potentiometer wire is
The magnetic field due to a current carrying circular coil on its axis at a distance of \(\sqrt{2} d\) from the centre of the coil is B. If d is the diameter of the coil, then the magnetic field at the centre of the coil is
The magnetic field at a point P on the axis of a short bar magnet of magnetic moment M is B. If another short bar magnet of magnetic moment 2M is placed on the first magnet such that their axes are perpendicular and their centres coincide. The resultant magnetic field at the point P due to both the magnets is
A string vibrates in its fundamental mode when a tension \(T_1\) is applied to it. If the length of the string is decreased by 25% and the tension applied is changed to \(T_2\), the fundamental frequency of the string increases by 100%, then \(\frac{T_2}{T_1}=\)
If a particle of mass 10 mg and charge 2 µC at rest is subjected to a uniform electric field of potential difference 160 V, then the velocity acquired by the particle is
An object of height 3.6 cm is placed normally on the principal axis of a concave mirror of radius of curvature 30 cm. If the object is at a distance of 10 cm from the principal focus of the mirror, then the height of the real image formed due to the mirror is
Monochromatic light of wavelength 6000 Å incidents on a small angled prism. If the angle of the prism is 6°, the refractive indices of the material of the prism for violet and red lights are respectively 1.52 and 1.48, then the angle of dispersion produced for this incident light is
A sound wave of frequency 210 Hz travels with a speed of 330 ms⁻¹ along the positive x-axis. Each particle of the wave moves a distance of 10 cm between the two extreme points. The equation of the displacement function (s) of this wave is (x in metre, t in second)
Four electric charges 2 µC, Q, 4 µC and 12 µC are placed on x-axis at distances x = 0, 1 cm, 2 cm and 4 cm respectively. If the net force acting on the charge at origin is zero, then Q =
In Young's double slit experiment, if the distance between 5th bright and 7th dark fringes is 3 mm, then the distance between 5th dark and 7th bright fringes is
The power of a refrigerator that can make 15 kg of ice at 0 °C from water at 30 °C in one hour is
To increase the length of a metal rod by 0.4%, the temperature of the rod is to be increased by (Coefficient of linear expansion of the metal = \(20 \times 10^{-6}\) °C⁻¹)
An air bubble rises from the bottom to the top of a water tank in which the temperature of the water is uniform. The surface area of the bubble at the top of the tank is 125% more than its surface area at the bottom of the tank. If the atmospheric pressure is equal to the pressure of 10 m water column, then the depth of water in the tank is