A nucleus 11Na²⁴ emits a beta particle to change into Magnesium (Mg):

i) Write the symbolic equation for the process.

ii) What are numbers 24 and 11 called?

In a cathode ray tube state:

i) the purpose of covering cathode by thorium and carbon.

ii) the purpose of the fluorescence screen

The adjacent diagram shows three different modes of vibrations P, Q and R of the same string.

                                   

i) Which vibrations will produce a louder sound and why? 

ii) The sound of which string will have maximum shrillness?

iii) State the ratio of wavelengths of P and R.

44.

i) State one important property of waves used for echo depth sounding.

ii) A radar sends a signal to an aircraft at a distance of 30 km away and receives it back after 2 × 10⁴ second. What is the speed of the signal?

Two resistors of 4 ohm and 6 ohm are connected in parallel to a cell to draw 0.5 A current from the cell.

i) Draw a labeled circuit diagram showing the above arrangement.

Heat energy is supplied at a constant rate to 100 g of ice at 0^o C. The ice is converted into water at 0^o C in 2 minutes. How much time will be required to raise the temperature of water from 0^o C to 20^o C. 

Specific Heat Capacity of substance A is 3.8 J g^-1 K^-1 whereas the specific heat capacity of substance B is 0.4 J g^-1 K T^-1.

i) Which of the two is a good conductor of heat?

ii) How is one led to the above conclusion?

iii) If substances A and B are liquids then which one would be more useful in car radiators? 

i) State any two measures to minimize the impact of global warming.