The frequency of revolution of the electron in Bohr's orbit varies with \(n\), the principal quantum number as _______.

In an experiment, a small steel ball falls through a Iiquid at a constant speed of \(10\, cm/s\). If the steel ball is pulled upward with a force equal to twice its effective weight, how fast will it move upward ? ......... \(cm/s\)

If the time period \(t\) of the oscillation of a drop of liquid of density \(d\), radius \(r\), vibrating under surface tension \(s\) is given by the formula \(t = \sqrt {{r^{2b}}\,{s^c}\,{d^{a/2}}} \) . It is observed that the time period is directly proportional to \(\sqrt {\frac{d}{s}} \) . The value of \(b\) should therefore be

Identify the correct truth table of the given logical circuit.

A particle of mass \(M\) is moving in a circle of fixed radius \(R\) in such a way that its centripetal acceleration at time \(t\) is given by \(n^2Rt^2\) where \(n\) is a constant. The Power delivered to the particle by the force acting on it, is

A steel rail of length \(5\,m\) and area of cross-section \(40\,cm^2\) is prevented from expanding along its length while the temperature rises by \(10\,^oC\). If coefficient of linear expansion and Young's modulus of steel are \(1.2\times10^{-5}\, K^{-1}\) and \(2\times10^{11}\, Nm^{-2}\) respectively, the force developed in the rail is approximately

Earth has mass 8 times and radius 2 times that of a planet. If the escape velocity from the earth is \(11.2 \mathrm{~km} / \mathrm{s}\), the escape velocity in \(\mathrm{km} / \mathrm{s}\) from the planet will be :

An electron is released from rest near an infinite non-conducting sheet of uniform charge density ' \(-\sigma\) '. The rate of change of de-Broglie wave length associated with the electron varies inversely as \(\mathrm{n}^{\text {th }}\) power of time. The numerical value of \(n\) is ________.

Given below are two statements: one is labelled as Assertion \(\mathrm{A}\) and the other is labelled as Reason \(\mathrm{R}\) Assertion A : The kinetic energy needed to project a body of mass m from earth surface to infinity is \(\frac{1}{2} \mathrm{mgR}\), where R is the radius of earth.
Reason \(\mathrm{R}\) : The maximum potential energy of a body is zero when it is projected to infinity from earth surface.
In the light of the above statements, choose the correct answer from the option given below

Two resistance of \(100\ \Omega\) and \(200\  \Omega\) are connected in series with a battery of \(4 \mathrm{~V}\) and negligible internal resistance. \(A\) voltmeter is used to measure voltage across \(100 \Omega\) resistance, which gives reading as \(1 \mathrm{~V}\). The resistance of voltmeter must be _______ \(\Omega\).

When a certain photosensitive surface is illuminated with monochromatic light of frequency \(v\) , the stopping potential for the photo current is \(-V_0/2.\) When the surface is illuminated by monochromatic light of frequency \(v/2,\) the stopping potential is \(-V_0.\) The threshold frequency for photoelectric emission is