Number of photons of equal energy emitted per second by a 6 mW laser source operating at 663 nm is ___________.
(Given: \(h=6.63\times10^{-34}\) J.s and \(c=3\times10^{8}m/s\))

\(LED\) is constructed from \(Ga-As-P\) semiconducting material. The energy gap of this \(LED\) is \(1.9\, eV\). Calculate the wavelength of light emitted and its colour. \(\left[ h =6.63 \times 10^{-34} \;Js \right.\) and \(\left. c =3 \times 10^{8}\; ms ^{-1}\right]\)

The moment of inertia of semicircular ring about an axis, passing through the center and perpendicular to the plane of ring, is \(\frac{1}{ x } MR ^2\), where \(R\) is the radius and \(M\) is the mass of semicircular ring. The value of \(x\) will be \(...........\)

A plane is inclined at an angle \(\alpha  = 30^o\) with respect to the horizontal. A particle is projected with a speed \(u = 2\,ms^{-1},\) from the base of the plant, making an angle \(\theta = 15^o\) with respect to the plane as shown in the figure. The distance from the base at which the particle hits the plane is close to  ........ \(cm\) (Take \(g = 10\,ms^2\) )

The value closest to the thermal velocity of a Helium atom at room temperature \((300\,K)\)in \(ms^{-1}\) is \([k_B\, = 1 .4\times10^{-23}\,J/K;\, m_{He}\, = 7\times10^{-27}\,kg]\)

The current sensitivity of moving coil galvanometer is increased by \(25 \%\). This increase is achieved only by changing in the number of turns of coils and area of cross section of the wire while keeping the resistance of galvanometer coil constant. The percentage change in the voltage sensitivity will be \(...........\%\)

The refractive index of a transparent liquid filled in an equilateral hollow prism is \(\sqrt{2}\). The angle of minimum deviation for the liquid will be

A spherical interface lens of radius \(R\) separates two media of refractive indices \(1\) and \(1.4\) respectively as shown in the figure below. A point source is placed at a distance of \(4R\) in front of spherical interface. The magnitude of the magnification of point source image is _______.

As shown in the figure, in an experiment to determine Young's modulus of a wire, the extension-load curve is plotted. The curve is a straight line passing through the origin and makes an angle of \(45^{\circ}\) with the load axis. The length of wire is \(62.8\,cm\) and its diameter is \(4\,mm\). The Young's modulus is found to be \(x \times\) \(10^4\,Nm ^{-2}\). The value of \(x\) is

A reversible heat engine converts one-fourth of the heat input into work. When the temperature of the sink is reduced by \(52\, K\), its efficiency is doubled. The temperature in Kelvin of the source will be ...... .

The dimensional formula of angular impulse is _______.

In Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at \(10.2 \mathrm{~V}\). The wavelength of light emitted by hydrogen atom when excited to the first excitation level is _______ \(\mathrm{nm}\). \(\left(\right.\) Given \(\mathrm{hc}=1245 \mathrm{eV} \mathrm{nm}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}\) ).

The coefficient of static friction between a wooden block of mass \(0.5\, kg\) and a vertical rough wall is \(0.2\) The magnitude of horizontal force that should be applied on the block to keep it adhere to the wall will be \(N\) \(\left[ g =10\, ms ^{-2}\right]\)