A biconvex lens of refractive index \(1.5\) has a focal length of \(20 \mathrm{~cm}\) in air. Its focal length when immersed in a liquid of refractive index \(1.6\) will be:

The displacement of a particle executing SHM is given by \(x=10 \sin \left(\omega t+\frac{\pi}{3}\right) \mathrm{m}\). The time period of motion is \(3.14 \mathrm{~s}\). The velocity of the particle at \(\mathrm{t}=0\) is_________ \(\mathrm{m} / \mathrm{s}\).

Two plane mirrors are inclined to each other such that a ray of light incident to the first mirror \((M_1)\) and parallel to the second mirror \((M_2)\) is finally reflected from the second mirror \((M_2)\) parallel to the first mirror \((M_1).\) The angle between the two mirrors will be......\(^o\)

A point source is kept at the center of a spherically enclosed detector. If the volume of the detector increased by 8 times, the intensity will

Given below are two statements: One is labelled as Assertion \((A)\) and the other is labelled as Reason \((R).\) Assertion \((A)\) : In an uniform magnetic field, speed and energy remains the same for a moving charged particle. Reason \((R)\) : Moving charged particle experiences magnetic force perpendicular to its direction of motion.

At time \(\mathrm{t}=0\) magnetic field of \(1000\) Gauss is passing perpendicularly through the area defined by the closed loop shown in the figure. If the magnetic field reduces linearly to \(500\) Gauss, in the next \(5 \;\mathrm{s}\), then induced \(EMF\) in the loop is ........\( \mu \mathrm{V}\)

Using equipartition of energy, the specific heat (in \(J\, kg^{-1}\, K^{-1}\) ) of aluminium at room temperature can be estimated to be ( atomic weight of aluminium \(= 27\))

A \(30\) cm long solenoid has \(10\) turns per cm and area of \(5\) cm\(^2\). The current through the solenoid coil varies from \(2\) A to \(4\) A in \(3.14\) s. The e.m.f. induced in the coil is \(\alpha\times 10^{-5}\) V. The value \(\alpha\) is ________.

The value of acceleration due to gravity at Earth’s surface is \(9.8\, m\,s^{-2}\). The altitude above its surface at which the acceleration due to gravity decreases to \(4.9\, m\,s^{-2}\), is close to: (Radius of earth \(= 6.4\times10^6\, m\))

A \(27\, mW\) lager beam has a cross -sectional area of \(10\, mm^2\). The magnitude of the maximum electric field in this electromagnetic wave is given by:........\(kV/m\) [Given permittivity of space \({ \in _0} = 9 \times {10^{ - 12}}\, SI\, units\), speed of light \(c = 3 \times 10^8\, m/s\)]

In \(LC\) circuit the inductance \(\mathrm{L}=40\; \mathrm{mH}\) and capacitance \(\mathrm{C}=100\; \mu \mathrm{F} .\) If a voltage \(\mathrm{V}(\mathrm{t})=10 \sin (314 \mathrm{t})\) is applied to the circuit, the current in the circuit is given as 

Two identical thin biconvex lenses of focal length \(15\, cm\) and refractive index \(1.5\) are in contact with each other. The space between the lenses is filled with a liquid of refractive index \(1.25\). The focal length of the combination is \(cm\).