Physics Test - ...

Consider an excited hydrogen atom in state n moving with a velocity v (v<< c). It emits a photon in the direction of its motion and changes its state to a lower state m. Apply momentum and energy conservation principle to calculate the frequency v of the emitted radiation. Compare this with the frequency v₀ emitted if the atom were at rest.

Two thin equiconvex lenses, each of focal length \(0.2\) m, are placed coaxially with their optic centres \(0.5\) m apart. What is the focal length of the combination?

A body of \(5\) kg is moving with a velocity of \(20 \) m/s. If a force of \(100\) N is applied on it for \(10\) s in the same direction as its velocity, what will now be the velocity of the body?

As per given figure \(A, B\) and \(C\) are the first, second and third excited energy levels of hydrogen atom respectively. If the ratio of the two wavelengths (. i.e. \(\frac{\lambda_1}{\lambda_2}\) ) is \(\frac{7}{4 \mathrm{n}}\), then the value of \(\mathrm{n}\) will be_________.

If \(v=\frac{A}{t}+B t^{2}+C t^{3}\) where \(v\) is velocity, \(t\) is time and \(A, B\) and \(C\) are constants, then the dimensional formula of \(B\) is:

A small hole of area of cross-section 2 mm² is present near the bottom of a fully filled open tank of height 2 m. Taking g = 10 m/s², the rate of flow of water through the open hole would be nearly

The magnitude of the magnetic field at the center of an equilateral triangular loop of side 1m which is carrying a current of 10 A is :

\(\left[\right.\) Take \(\mu_0=4 \pi \times 10^{-7} \mathrm{NA}^{-2}\) ]

A body cools from \(80^{\circ} C\) to \(60^{\circ}\) in 5 minutes. The temperature for the surrounding is \(20^{\circ} C\). The time it takes to cool from \(60^{\circ} C\) to \(40^{\circ} C\) is