Electromagnetic Waves — Physics STD 12 Science — Question

Classify metals, conductors and semiconductors.

What is space wave propagation? State the factors which limit its range of propagation. Derive an expression for the maximum line of sight distance between two antennas for space wave propagation.

Explain principle, construction and working of optical fibre.

Write and explain principle of superposition for stationary electric forces.

Characteristic X-rays may be used to identify the element from which they are being emitted. Can continuous X-rays be used for this purpose?

Using Gauss’s theorem, show mathematically that for any point outside the shell, the field due to a uniformly charged thin spherical shell is the same as if the entire charge of the shell is concentrated at the centre. Why do you expect the electric field inside the shell to be zero according to this theorem?

With the help of a simple diagram, explain the working of a silicon solar cell, giving all three basic processes involved. Draw its I-V characteristic.

A concave mirror has a focal length of 20cm. Find the position or positions of an object for which the imagesize is double of the object-size.

1. Define current sensitivity of a galvanometer. Write its expression.
2. A galvanometer has resistance G and shows full scale deflection for current Ig.

1. How can it be converted into an ammeter to measure current up to I₀(I₀ > Ig)?
2. What is the effective resistance of this ammeter?

A ball is given a speed v on a rough horizontal surface. The ball travels through a distance l on the surface and stops.

1. What are the initial and final kinetic energies of the ball?
2. What is the work done by the kinetic friction?