Which one of the following particles in the nucleus of an atom was discovered by J. Chadwick?
- A.Electron
- B.Proton
- C.Positron
- D.Neutron
Correct answer
Explanation
The correct answer is D, Neutron. James Chadwick discovered the neutron in 1932, the uncharged particle that sits in the nucleus alongside the proton.
Chadwick bombarded beryllium with alpha particles and found that it gave off a penetrating radiation of neutral particles with a mass almost equal to that of a proton. This explained why atomic mass is larger than the number of protons alone would suggest, and it later made nuclear fission possible, since neutrons can enter a nucleus without being repelled. He received the Nobel Prize in Physics in 1935 for this work.
A, the electron, was discovered by J. J. Thomson in 1897 and lives outside the nucleus.
B, the proton, is credited to Ernest Rutherford, whose experiments around 1919 identified it in the nucleus.
C, the positron, the antiparticle of the electron, was found by Carl Anderson in cosmic rays in 1932 and is not a nuclear constituent.
Exam tip: electron, Thomson (1897); proton, Rutherford; neutron, Chadwick (1932); nucleus, Rutherford (1911).
Practice Questions
View allWhich one of the following cell organelles contains DNA?
- A.Golgi apparatus
- B.Mitochondrion
- C.Lysosome
- D.Endoplasmic reticulum
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Mitochondria carry their own small, circular DNA and their own ribosomes. Mitochondria are the powerhouses of the cell, where aerobic respiration makes ATP.
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
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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
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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
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These are the three main divisions of the human brain. The fore brain is the largest part.
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