Rutherford's alpha-particle scattering experiment was responsible for the discovery of
- A.Electron
- B.Proton
- C.Nucleus
- D.Helium
Correct answer
Explanation
The correct answer is C, Nucleus. Rutherford's gold foil experiment showed that an atom's positive charge and almost all its mass sit in a tiny central nucleus.
In 1909 Hans Geiger and Ernest Marsden, working under Rutherford, fired alpha particles at a very thin gold foil. Most passed straight through, showing the atom is mostly empty space; a few were deflected, and about one in 20,000 bounced almost straight back. Rutherford explained in 1911 that this could happen only if the positive charge was packed into a very small, dense centre, which he called the nucleus, with electrons moving around it. This replaced Thomson's plum pudding model.
A is wrong because the electron was discovered by J.J. Thomson in 1897 using cathode rays.
B is wrong because the proton was identified separately, when Rutherford knocked it out of nitrogen nuclei in 1917–19, not in the scattering experiment.
D is wrong because helium was not discovered here; alpha particles are themselves helium nuclei.
Exam tip: electron – Thomson (1897), nucleus – Rutherford (1911), neutron – Chadwick (1932).
Practice Questions
View allWhich one of the following cell organelles contains DNA?
- A.Golgi apparatus
- B.Mitochondrion
- C.Lysosome
- D.Endoplasmic reticulum
Show answer
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Read the full explanation →Which set of vegetables is underground stem or modified stem of a plant?
- A.Potato, artichoke, round gourd
- B.Onion, garlic, carrot
- C.Potato, onion, garlic
- D.Potato, garlic, turnip
Show answer
All three are underground modified stems: the potato is a stem tuber, and onion and garlic are bulbs. A stem can be told from a root by its nodes and buds.
Read the full explanation →A sound wave having frequency of 300 Hz is travelling in an unknown medium. Its wavelength is not known. It travels a distance equal to 150 times its wavelength in time t. The value of t is :
- A.0.5 s
- B.1 s
- C.1.5 s
- D.2 s
Show answer
A wave moves forward by one wavelength in each cycle, so 150 wavelengths take 150 cycles, and 150 cycles at 300 per second take half a second.
Read the full explanation →A body floats in a liquid if the buoyant force is :
- A.equal to its weight.
- B.less than its weight.
- C.greater than its weight.
- D.zero.
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A floating body is in equilibrium, so the upward buoyant force exactly balances its weight. By Archimedes' principle, a body in a liquid is pushed up by a force equal to the weight of the liquid it displaces.
Read the full explanation →Which of the following are the different parts of a human brain ?
- A.Forefront brain, Standard brain and Hind brain
- B.Fore brain, Median brain and Rear brain
- C.Fore brain, Mid brain and Hind brain
- D.Precursor brain, Mean brain and Hind brain
Show answer
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Read the full explanation →