1.What is displacment current?

The displacement current can be defined as the current which comes into play in the region in which the electric field (or the electric flux) is changing with time.

2.What are electromagnetic waves?

Electromagnetic waves are nonmechanical waves which move with speed equals to the speed of light (in vacuum).

It is a transverse wave.

3.What is meant by fraunhoufer lines?

When the spectrum obtained from the Sun is examined, it consists of large number of dark lines (line absorption spectrum). These dark lines in the solar spectrum are known as Fraunhofer lines

4.Give two uses each of (i) IR radiation, (ii) Microwaves and (iii) UV radiation.

(i) IR radiation

• It provides electrical energy to satellites by means of solar cells.
• It is used to produce dehydrated fruits,
• in green houses to keep the plants warm,
• heat therapy for muscular pain or sprain,
• TV remote as a signal carrier,
• to look through haze fog or mist
• used in night vision or infrared photography.

(ii) Microwaves

• It is used in radar system for aircraft navigation, speed of the vehicle,
• microwave oven for cooking and
• Very long distance wireless communication through satellites.

(iii) UV radiation

• It is used to destroy bacteria in sterilizing the surgical instruments,
• burglar alarm,
• to detect the invisible writing, finger prints
• and also in the study of atomic structure.

5.Give uses of X-Ray ?

X-rays are used extensively in studying structures of inner atomic electron shells and crystal structures. It is used in detecting fractures, diseased organs, formation of bones and stones, observing the progress of healing bones. Further, in a finished metal product, it is used to detect faults, cracks, flaws and holes.

6.Give uses of Gamma rays-Ray ?

It is used in radio therapy for the treatment of cancer and tumour, in food industry to kill pathogenic microorganism.

7.Write down the integral form of modified Ampere’s circuital law?

The total current enclosed by the surface becomes the sum of conduction current and displacement current.