Physics: 2017: CBSE: [Delhi]: Set – III

There is no change in the magnetic flux linked with the circular loop so there will be no induced emf in the loop. This happened because magnetic field lines are parallel to the plane of the loop.

The angle between the field line and the area vector is 90^o and we know that

The ratio of peak value of electric and magnetic fields gives the speed of the electromagnetic waves, c in vacuum which is given as

The given I-V characteristics is of a solar cell.

The horizontal component of the magnetic field is given by

All the charge given to the spheres whether it is hollow or solid will appear on the outer surface of the spheres, so the charge given to a metallic sphere does not depend on whether it is hollow or solid.

Distance of closest approach: When an alpha particle moves towards the nucleus, its kinetic energy keeps on decreasing because kinetic energy is being consumed in doing work against the force of repulsion of the nucleus. The distance from the nucleus at which velocity of an alpha particle becomes zero is known as the distance of closest approach.

Distance of closest approach,r₀ is given as

Following are the two important limitations of Rutherford nuclear model of the atom:

1. According to the classical electromagnetic theory, the revolving electron should radiate energy. An electron pursuing a curved path is accelerated and therefore, it should continuously loose energy while rapidly spiralling into the nucleus.

2. It could not explain the emission line spectrum of the hydrogen atom. As per classical electromagnetic theory, the frequency of EM waves emitted by revolving electron should be equal to the frequency of revolution.Thus, it would emit a continuous spectrum, in contradiction to the observed line spectrum.

Two point objects are said be just resolved when the central maximum of the diffraction pattern of one lies on the first secondary minimum of the other.

If two point objects placed close to each other are seen through optical instruments, their images or their diffraction patterns might overlap each other.If the overlapping is small, both the point objects are seen as separate and the instrument is said to resolve the two point objects.But if the overlapping is large, the two point objects are not seen as separate and the optical instrument is not able to resolve the two objects.

The formula for resolving power of compound microscope is given by .

The resolving power of the compound microscope can be increased by

1. Decreasing the wavelength () of the light used.

2. Increasing the refractive index (n) of the medium.

(i)Line of sight communication is a type of propagation that can transmit and receive data only where transmit and receive stations are in view of each other without any sort of an obstacle between them. Few examples of line of sight communication are FM radio, microwave and satellite transmission.

(ii)Sky wave propagation is used for short wave broadcast services. It makes communication easier over great distances using simple equipments. It cannot be used for transmission of TV signals, as waves with frequency more than 40 megahertz cannot be reflected back to the earth by ionosphere. Transmission of TV signal is done with the help of radio waves of frequency ranging between 80 MHz and 200 MHz.

The covering range (d) for an antenna of height 'h' is , where R is radius of the earth.

We know that,

Charge on the proton = e

Charge on the alpha particle = 2e

Let mass of proton = m

So, mass of alpha particle = 4m

When a particle is of mass m and charge q is accelerated by a potential V, then its de Broglie wavelength is given by