The hydrogen bomb and the uranium bomb are based, respectively on
- A.nuclear fusion and fission
- B.fission and thermonuclear fusion
- C.geothermal fission and fusion
- D.geothermal fusion and fission
Correct answer
Explanation
The correct answer is A, nuclear fusion and fission. A hydrogen bomb fuses light hydrogen nuclei, while a uranium bomb splits heavy uranium-235 nuclei.
In nuclear fission a heavy nucleus such as uranium-235 absorbs a neutron and splits into two lighter nuclei, releasing energy and two or three more neutrons. These neutrons split more nuclei in a chain reaction, which an atom bomb lets run out of control; the bomb dropped on Hiroshima in 1945 was a uranium bomb of this kind. In nuclear fusion, isotopes of hydrogen such as deuterium and tritium join to form helium. Fusion needs temperatures of millions of degrees, so a hydrogen bomb uses a fission bomb as its trigger, which is why it is called a thermonuclear weapon. The Sun also shines by fusion.
B is wrong because it reverses the two processes. C is wrong because 'geothermal' refers to the Earth's internal heat, not to bombs, and the order is also wrong. D is wrong because geothermal energy has nothing to do with either weapon.
Exam tip: Atom bomb and nuclear reactors: fission; hydrogen bomb and the Sun: fusion.
Practice Questions
View allWhich one of the following is the purest form of Carbon ?
- A.Charcoal
- B.Coke
- C.Fullerene
- D.Carbon black
Show answer
Fullerenes are made of carbon atoms alone, with no surface to trap other substances, so they are counted as the purest form of carbon.
Read the full explanation →A planet has a mass M₁ and radius R₁. The value of acceleration due to gravity on its surface is g₁. There is another planet 2, whose mass and radius both are two times that of the first planet. Which one of the following is the acceleration due to gravity on the surface of planet 2?
- A.g₁
- B.2g₁
- C.g₁/2
- D.g₁/4
Show answer
Surface gravity is g = GM/R², so doubling the mass doubles g while doubling the radius divides it by four, leaving g₁ × 2/4 = g₁/2.
Read the full explanation →Which one of the following is the major constituent of biogas ?
- A.Carbon dioxide
- B.Nitrous oxide
- C.Methane
- D.Oxygen
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Methane makes up the largest share of biogas, usually about 55 to 75 per cent, and it is the gas that burns.
Read the full explanation →A lemon kept in water in a glass tumbler appears to be larger than its actual size. It is because of
- A.reflection of light
- B.scattering of light
- C.refraction of light
- D.polarization of light
Show answer
The lemon looks bigger because light from it bends as it passes from water through the curved glass into air.
Read the full explanation →Which one of the following conclusions could not be derived from Rutherford's α-particle scattering experiment?
- A.Most of the space in the atom is empty.
- B.The radius of the atom is about 10⁵ times the radius of the nucleus.
- C.Electrons move in a circular path of fixed energy called orbits.
- D.Nearly all the mass of the atom resides in the nucleus.
Show answer
. Orbits of fixed energy were proposed by Niels Bohr in 1913; Rutherford's experiment said nothing about the energy of electrons.
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