Physics NCERT Exemplar Solutions Class 12th Chapter Nine

Find the modulation index of an AM wave having 8V variation where maximum amplitude to the wave is 9V.

Find the ratio of energies of photos product due to transition of an electron of hydrogen atom from its (i) second permitted energy level to the first level. and (ii) the highest permitted energy level to the first permitted level.

The kinetic energy of emitted electron is E when the right incident on the metal has wavelength $\lambda$ . To double the kinetic energy, the incident light must have wavelength:

Match List – I with List – II:

List – I List – II

(A) UV rays (i) Diagnostic tool in medicine

(B) X-rays(ii) Water purification

(C) Microwave(iii) Communication, Radar

(D) Infrared wave(iv) Improving visibility in foggy daya

Choose the correct answer from the options given below:

A coil of inductance 1H and resistance 100 $\Omega$ is connected to a battery of 6.V. Determine approximately:

(A)The time elapsed before the current acquires half of its steady – state value.

(B)The energy stored in the magnetic field associated with the coil at instant 15ms after the circuit is switched on. (Given In 2 = 0.693, e3/2 = 0.25)

An alternating emf E = 440 sin 100t is applied to a circuit containing an inductance of $\frac{\sqrt[]{2}}{\pi }H.$ If an a.c. ammeter is connected in the circuit, its reading will be:

Two metallic wires of identical dimensions are connected in series. If ${\sigma }_{1}and{\sigma }_2$ are the conductivities of these wires respectively, the effective conductivity of the combination is:

Given below are two statements.

Statement I : Electric potential is constant within and at the surface of each conductor.

Statement II : Electric field just outside a charged conductor is perpendicular to the surface of the conductor at every point.

In the light of the above statements, choose the most appropriate answer from the options given below.

A spherically symmetric charge distribution is considered with charge density varying

as $\rho \left(r\right)=\{\begin{array}{cc}\hfill {\rho }_0\left(\frac{3}{4}-\frac{r}{R}\right)for\hfill & \hfill r\le R\hfill \\ \hfill zero\hfill & \hfill forr>R\hfill \end{array}$

Where, r(r < R) is the distance from the centre O (as shown in figure). The electric field at point P will be:

The distance between an object and a screen is $100\mathrm{c}\mathrm{m}$ . A lens can produce real image of the object on the screen for two different positions between the screen and the object.

The distance between these two positions is $40\mathrm{c}\mathrm{m}$ . If the power of the lens is close to $\left(\frac{\mathrm{N}}{100}\right)\mathrm{D}$ where $\mathrm{N}$ is an integer, the value of $\mathrm{N}$  is