Sea water at frequency \(v=4\times { 10 }^{ 8 }\)Hz has permittivity \(\varepsilon \ \approx \ 80 \ { \varepsilon }_{ 0 }\),  permeability \(\mu ={ \mu }_{ 0 }\) and resistivity \(\rho =0.25 \ \Omega -m\) Imagine a parallel plate capacitor immersed in sea water and driven by an alternating voltage source  \(v(t) \ = \ { V }_{ 0 } \ sin \ (2\pi vt)\) . What fraction of the conduction current density is the displacement current density?

Discuss the quantitative production of electromagnetic waves when a charge is accelerated.

What are the uses of electromagnetic waves?

A parallel plate capacitor made of circular plates each of radius R = 5.0 cm has a capacitance C = 96 pF. The capacitor is connected to a 220 V a.c supply with (argular) frequency of 300 rad \({ s }^{ -1 }\) .

A radio can be tuned to any station in the 6 MHz to MHz band. What is the corresponding wavelength between 6 MHz and 9 MHz?

Four persons went on an excursion on a hilltop where the temperature was quite low. one of them fell sick. The other persons put a blanket on him, collected the pieces of dry wood and ignited a fire in his vicinity. After some time the sick person felt better
Read the above passage and answer the following question
(i) What is the type of rays coming from fire?
(ii) Why did the sick person feel better while seating near the fire?
(iii) What basic values do you learn from this study?

Draw a labelled diagram of Hertz's experiment. Explain how electromagnetic radiations are produced using this set-up.

Saurabh reads in his text book that if the distance from the bulb is double then intensity is reduced to one-fourth. But then he notices that as a laser beam travel across the length of a room, its intensity is essentially constant. So he wants to know what geometrical characteristic of laser beam is responsible for the constant intensity, which is missing in the case of light from the bulb. His friend Samir explained him such things properly.
(a) What value are displayed by Samir?
(b) How does Samir explain such things properly?

Chirag was at the restaurant chatting with his cousins. The restaurant was clean and free of files and insects to his relief. His cousin was curious to know about the UV lamp in the corner and asked Chirag about it. Chirag explained that inside the fluorescent lamp, the electrical energy is converted into UV radiation. The inside of the tubes is coated with a fluorescent powder which absorbs the UV and emits violet light in the visible region. These attract the insects which are electrocuted by high-voltage wires near the lamp, so that don't fall on the food and contaminate them.
(a) Name the main source of UV rays?
(b) Why are they considered harmful to us?
(c) What impressed you about chirag?

Police came to know that were some valuable articles which got stolen from the museum. In a search operation, police arrested the thief with stolen articles. Now the police wanted to prove the case, so police contacted Raman who helped and confirmed that the stolen articles belong to the museum using UV light.
(a) What are the values exhibited by Raman? 
(b) How does he prove such case?