Physics Questions

The water rise in a capillary tube dipped in water is such that the weight of water in the tube above the surface of water in the vessel is equal to (balances) the upward force due to surface tension. So it is clear that if the the bore (radius) to the tube is decreased, the height of the water column in it must be greater.  So, (a) is correct.

It will stop at a height where the weight of the balloon with contents is equal to the weight of air displaced by it, i.e , when the upthrust is equal to the downthrust. The question of bursting will depend on how much difference of pressure inside and outside , the material of the balloon can withstand. It is assumed the balloon is filled with a lighter than air gas like hydrogen or helium.

The lux (lx) is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square meter.

To produce controlled energy i.e energy at a controlled or steady rate, the number of fissions per second must be controlled and maintained at that rate. Excess neutrons should be absorbed by control roads like cadmium.

The resistance of metallic conductors e.g, platinum, increases with rise of  temperature . The increase in temperature results in a decrease of current which can be recorded in a galvanometer if the conductor is included in an electrical circuit. Thus the temperature can be known; platinum resistance thermometer is used generally for accurate scientific work. When two dissimilar metals are joined at the ends, and these ends are subjected to a difference of temperature, a current flows through the metals. Greater the difference of temperature , greater the current. So the curent strength can form the basis for measuring the difference in temperature. And when one of these temperatures is known, we can calculate the other.

A modem is nothing but short for Modulator and Demodulator. It is used mostly for connecting to the internet.

A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves.

RADAR - RAdio Detection And Ranging.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. 

Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.