List of top Physics Questions

For sodium light, the two yellow lines occur at $\lambda _{1}$ and $\lambda _{2}$ wavelengths. If the mean of these two is $6000 \, \overset{^\circ }{A}$ and $\left|\lambda _{2} - \lambda _{1}\right|=6 \, \overset{^\circ }{A}$ , then the approximate energy difference between the two levels corresponding to $\lambda _{1}$ and $\lambda _{2}$ is
If proton and a - particle are accelerated by the same potential $V$ . Then, the ratio of their wavelengths $\lambda _{\text{P}}:\lambda _{\alpha }$ would be
The energy (in $eV$ ) required to excite an electron from $n=2$ to $n=4$ state in hydrogen atom is
Two radioactive substances $A$ and $B$ have decay constants $5\lambda $ and $\lambda $ respectively. At $ \, t=0$ , a sample has the same number of the two nuclei. The time taken for the ratio of the number of nuclei to become $\left(\frac{1}{e}\right)^{2}$ will be
An $H$ -atom moving with speed $v$ makes a head-on collision with another $H$ -atom at rest. Both the atoms are in the ground state. The minimum value of velocity $v$ for which one of the atoms may excite is
If the wavelenth of $K_{\alpha }$ radiation emitted by an atom of atomic number $Z=41$ is $\lambda $ , then the atomic number for an atom that emits $K_{\alpha }$ radiation with wavelength $4$ $\lambda $ , is
Electromagnetic waves were first of all produced in the laboratory by
The wavelength of electromagnetic waves produced by Hertz was about
The ratio of kinetic energy and the total energy of the electron in the $n^{th}$ quantum state of Bohr's atomic model of a hydrogen atom is
An electric charge in uniform motion produces
Electromagnetic waves are
Which among the following does not represent Maxwell's equation?
If $ \mu_{0}$ be the permeability and $\varepsilon_{0} $ be the permittivity of a medium, then its refractive index is given by
The requirement of transmitting microwaves from one position to another on the earth is that
How many geo-synchronous satellites are required to provide the communication over the whole part of the earth
In optical fibre communication system, light source can be
Filters are essential components to
Light emerging from the end of an optical fibre link must be detected and converted into electronic pulses for further processing so that
The height if geo-synchronous orbit from the surface of the earth is
Analog signal can be converted into digital signal and vice-versa with the help of a device called
A $10\, kW$ drilling machine is used to drill a bore in a small aluminium block of mass $8 \,kg$. Find the rise in temperature of the block in $2.5$ minutes, assuming $50\%$ power is used up in heating the machine itself or lost to the surroundings. (Specific heat of aluminium $= 0.91\, J \,g^{-1} \,^{\circ}C^{-1}$)
The $B-H$ curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with $1000 \, turns \, cm^{- 1}$ . The current that should be passed in the solenoid to demagnetise the ferromagnet completely is
The magnetic field at the point of intersection of diagonals of a square loop of side $L$ carrying a current $I$ is
Mixed $He^{+}$ and $O^{2 +}$ ions (mass of $H e^{+}=4 \, amu \, and \, that \, of \, O^{2 +}=16 \, amu$ ) beam passes a region of constant perpendicular magnetic field. If kinetic energy of all the ions is same, then
A $ 1\, kg $ block situated on a rough incline is connected to a spring of negligible mass having spring constant $ 100\, N\,m^{-1} $ as shown in the figure.
The block is released from rest with the spring in the unstretched position. The block moves $ 10\, cm $ down the incline before coming to rest. The coefficient of friction between the block and the incline is (Take $ g = 10\, ms^{-2} $ and assume that the pulley is frictionless)