notes prepared by subhankar Karmakar
Q1. What is scientific method? Mention the various steps involved in it.
Ans. Scientific method: the step-by-step approach used by a scientist in studying natural phenomena and establishing laws which govern these phenomena is called scientific method.
Generally, it involves the following steps:
a. Taking a large number of systematic observations by doing controlled experiments.
b. Studying these observations and making qualitative and quantitative reasoning.
c. Suggesting mathematical models to account for the observed behaviour.
d. Predicting new phenomena on the basis of suggested model.
e. Modifying the theory, if necessary, the light of fresh evidences.
Q2. Name the four basic forces in nature. Arrange them in the order of their increasing strengths.
Ans. Fundamental forces in nature:
In the macroscopic world, we observe several kinds of forces. All the forces between microscopic objects arise from two fundamental forces:
a. Gravitational force(Fg)
b. Electromagnetic force.
(Fe)
In the microscopic world, there are two more basic forces:
c. Strong nuclear force(Fs)
d. Weak nuclear force
(Fw)
(Fg) : (Fw) : (Fe) : (Fs) = 1: 10²⁵ : 10³⁶ : 10³⁸
Q3. Describe briefly the fundamental forces in nature.
Ans. There are four fundamental forces in nature. They are as follows:
a. Gravitational force(Fg)
b. Electromagnetic force. (Fe)
c. Strong nuclear force(Fs)
d. Weak nuclear force (Fw)
Gravitational force(Fg) : it is a force of mutual attraction between two bodies by virtue of their masses. According to the Newton's law of gravitation, the gravitational attraction between two bodies of masses m₁ and m₂ separated by a distance r is given by
Fg = Gm₁m₂/r²
Where G is the universal gravitational constant.
Electromagnetic force (Fe):
The force acting between two electric charges at rest is called electrostatic force. Electrostatic force is a part of electromagnetic force. According to Coulomb's law, the magnitude of the electrostatic force (Fe) between two point charges q₁ and q₂ separated by a distance r in vacuum is given by
(Fe) = (1/4πεₒ).q₁q₂ / r²
Where εₒ is the permittivity of vacuum.
The force acting between two magnetic poles is called magnetic force.
Together electrostatic force and magnetic force is known as electromagnetic force.
Weak nuclear force (Fw):
It is a force that appears only between elementary particles involved in a nuclear process such as the β-decay of a nucleus. It is a short range force that operates only over the size of a nucleus (= 10⁻¹⁵ m)
Strong nuclear force(Fs):
The strong attractive force which binds together the protons and neutrons in a nucleus is called strong nuclear force. It is a short range force that operates only over the size of a nucleus (= 10⁻¹⁵ m)
Q4. What are the different conservation laws in Physics?
Ans. Conservation laws: in any physical process involving the different forces, some physical quantities, remain unchanged with time. Such quantities are called conserved quantities. The laws which govern the conservation of these quantities are called conservation laws.
There are four basic conservation laws:
a. Law of conservation of energy.
b. Law of conservation of linear momentum
c. Law of conservation of angular momentum
d. Law of conservation of charge.
Q5. Name the scientist who was first awarded two Nobel prizes.
Ans. Madame Marie Curie , for physics ine 1903 and for chemistry in 1911.
Q6. Who first discovered radioactivity?
Ans. A H Becquerrel in 1896.
Q7. Mention some important contributions of Albert Einstein to physics.
Ans. a. Mass energy equivalence
b. Photoelectric effect
c. Special theory of relativity
d. General theory of relativity.
Q8. Name the Indian physicist who was first awarded the Nobel prize.
Ans. C V Raman.
Q9. What was the important discovery of CV Raman?
Ans. Inelastic scattering of light by molecules.
Q10. What was the major contribution of Indian physicist SN Bose?
Ans. Quantum statistics ( Bose Einstein statistics)
Q11. With which field work was the famous Indian physicist H J bhabha associated?
Ans. Cascade process in cosmic radiation.
Q12. Name the Indian physicist associated with the triple helical structure of proteins.
Ans. G N Ramachandran.
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