A nucleus of an atom consists of 146 neutrons and 95 protons. It decays after emitting an alpha particle. How many protons and neutrons are left in the nucleus after an alpha emission?

1. protons = 93, neutrons = 144
2. protons = 95, neutrons = 142
3. protons = 89, neutrons = 144
4. protons = 89, neutrons = 142

For a convex lens, the minimum distance between an object and its real image in terms of focal length (f) of a given lens must be:

1. 1.5 f
2. 2.5 f
3. 2 f
4. 4 f

Two sound waves X and Y have same amplitude and same wave pattern, but their frequencies are 60 Hz and 120 Hz respectively, then:

1. X will be shriller and Y will be grave
2. X will be grave and Y will be shriller
3. X will differ in quality than Y
4. X is louder than Y.

For burning of coal in a thermoelectric station, the energy conversion taking place is:

1. chemical to heat to mechanical
2. chemical to heat to mechanical to electrical
3. chemical to heat to light
4. heat to chemical to mechanical