John is trying to create musical notes using water-filled bottles, as shown in the picture.

Which of the bottles is likely to produce a musical note with the highest pitch? Give reasons.

When Shyam, the band leader, struck both the bass drum and the kettle drum with equal force, the bass drum emitted a sound measuring 120 dB, whereas the kettle drum produced a sound of 90 dB. Explain this discrepancy in the loudness.

There are two copper wires of length ratio 1:2 that have their cross-sectional areas in the ratio 1:4. What will be the ratio of their:

(a) resistances?
(b) specific resistances?

AB is an object and PQ is its real, inverted image. The lengths of AB and PQ are equal. This is possible when a lens is present between the object and its image.

(a) What kind of lens is used here? Also, state the position of the lens and where it is to be placed.

(b) Name a device where this lens action is used.