Waves of special frequencies are used for cleaning hard to reach places. Explain how do these waves perform this work.

What is the frequency range of radio waves? How are radio waves produced?

Which of the following frequencies will be suitable for beyond-the-horizon communication using the sky waves?

A sound wave creates oscillation in air at a place 1000 times in 100 secons. Find the time period and frequency.

Draw a labelled diagram of Hertz's experiment set up to produce electromagnetic waves. Explain the generation of electromagnetic waves using this set up.

What is an oscillator ? Draw a labelled circuit diagram for an oscillator using PNP transistor.What is the function of feed back coil in it ? Write an expression for the frequency of waves produced by it.What is the use of waves produced by it ?

The given circuit diagram shows a series LCR circuit connected to a variable frequency 230 V source. How do you explain the observations that the algebraic sum of the voltages across the three elements is greater than the supplied voltages?

How is a wavefront defined? Using Huygens' prniciple draw a figure showing the propagation of a plane wave refracting at a plane surface separating two media. Hence verify Snell's law of refraction.

For sound waves, the Doppler formula for frequency shift differs slightly between the two situations: 1. source at rest, observer moving 2. source moving, observer at rest. The exact Doppler formulas for the case of light waves in vacuum are, however, strictly identical for these situations. Explain why this should be so. Would you expect the formulas to be strictly identical for the two situations in case of light travelling in a medium?